Document ID: FERC-2022-0047-0001
Agency: ferc
Document Type: Rule
Title: Managing Transmission Line Ratings
Posted Date: 2022-01-13T05:00Z

[Federal Register Volume 87, Number 9 (Thursday, January 13, 2022)]
[Rules and Regulations]
[Pages 2244-2307]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-27735]

[[Page 2243]]

Vol. 87

Thursday,

No. 9

January 13, 2022

Part II

Department of Energy

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Federal Energy Regulatory Commission

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18 CFR Part 35

Managing Transmission Line Ratings; Final Rule

  Federal Register / Vol. 87, No. 9 / Thursday, January 13, 2022 / 
Rules and Regulations  

[[Page 2244]]

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DEPARTMENT OF ENERGY

Federal Energy Regulatory Commission

18 CFR Part 35

[Docket No. RM20-16-000; Order No. 881]

Managing Transmission Line Ratings

AGENCY: Federal Energy Regulatory Commission, Department of Energy.

ACTION: Final rule.

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SUMMARY: The Federal Energy Regulatory Commission (Commission) is 
revising both the pro forma Open Access Transmission Tariff and the 
Commission's regulations under the Federal Power Act to improve the 
accuracy and transparency of electric transmission line ratings. 
Specifically, the Commission is requiring: Public utility transmission 
providers to implement ambient-adjusted ratings on the transmission 
lines over which they provide transmission service; regional 
transmission organizations (RTO) and independent system operators (ISO) 
to establish and implement the systems and procedures necessary to 
allow transmission owners to electronically update transmission line 
ratings at least hourly; public utility transmission providers to use 
uniquely determined emergency ratings; public utility transmission 
owners to share transmission line ratings and transmission line rating 
methodologies with their respective transmission provider(s) and with 
market monitors in RTOs/ISOs; and public utility transmission providers 
to maintain a database of transmission owners' transmission line 
ratings and transmission line rating methodologies on the transmission 
provider's Open Access Same-Time Information System site or other 
password-protected website.

DATES: This rule will become effective March 14, 2022.

FOR FURTHER INFORMATION CONTACT: Dillon Kolkmann (Technical 
Information), Office of Energy Policy and Innovation, Federal Energy 
Regulatory Commission, 888 First Street NE, Washington, DC 20426, (202) 
502-8650, [email protected].
    Mark Armamentos (Technical Information), Office of Energy Market 
Regulation, Federal Energy Regulatory Commission, 888 First Street NE, 
Washington, DC 20426, (202) 502-8103, [email protected].
    Ryan Stroschein (Legal Information), Office of the General Counsel, 
Federal Energy Regulatory Commission, 888 First Street NE, Washington, 
DC 20426, (202) 502-8099, [email protected].

SUPPLEMENTARY INFORMATION:

Table of Contents

Paragraph Numbers

I. Introduction 1
II. Background 13
III. Need for Reform 17
    A. NOPR Proposal 17
    B. Comments 23
    C. Commission Determination 29
IV. Discussion 40
    A. Transmission Line Ratings Definition 40
    1. NOPR Proposal 40
    2. Comments 42
    3. Commission Determination 44
    B. Ambient-Adjusted Ratings 47
    1. AAR Definition and Transmission Provider Obligations 47
    2. Specific AAR Implementation Requirements 104
    3. Other AAR Implementation Issues 151
    C. Seasonal Line Ratings 193
    1. Seasonal Line Ratings Requirements 193
    2. Seasonal Line Rating Implementation Requirements 204
    D. Exceptions and Alternate Ratings 217
    1. NOPR Proposal 217
    2. Comments 219
    3. Commission Determination 227
    E. Dynamic Line Ratings 235
    1. Dynamic Line Ratings Definition 235
    2. DLR Requirements 240
    3. Extending to non-RTO/ISO Transmission Providers the 
Requirement To Allow Transmission Owners To Electronically Update 
Transmission Line Ratings at Least Hourly 256
    4. DLR Studies 259
    5. Advanced Transmission Technology Cost Recovery 265
    F. Emergency Ratings 267
    1. NOPR Request for Comments 267
    2. Emergency Ratings Definition and Implementation Requirements 
269
    3. Equipment for Which Emergency Ratings Must Be Calculated 304
    G. Transparency 306
    1. NOPR Proposal 306
    2. Comments 309
    3. Commission Determination 330
    H. Other Miscellaneous Issues 344
    1. Comments 344
    2. Commission Determination 346
    I. Compliance 348
    1. NOPR Proposal 348
    2. Comments 351
    3. Commission Determination 360
V. Information Collection Statement 364
VI. Environmental Analysis 383
VII. Regulatory Flexibility Act 384
VIII. Document Availability 399
IX. Effective Date and Congressional Notification 402
Appendix A: Abbreviated Names of Commenters
Appendix B: Pro Forma Open Access Transmission Tariff

I. Introduction

    1. In this final rule, the Federal Energy Regulatory Commission 
(Commission) is adopting reforms, pursuant to section 206 of the 
Federal Power Act (FPA),\1\ to the pro forma Open Access Transmission 
Tariff (OATT) and the Commission's regulations to improve the accuracy 
and transparency of electric transmission line ratings used by 
transmission providers.\2\ As discussed below, we adopt the 
Commission's proposal in the Notice of Proposed Rulemaking (NOPR) to 
define a transmission line rating as ``the maximum transfer capability 
of a transmission line, computed in accordance with a written 
transmission line rating methodology and consistent with Good Utility 
Practice,\3\ considering the technical limitations on conductors and 
relevant transmission equipment (such as thermal flow limits), as well 
as technical limitations of the Transmission System (such as system 
voltage and stability limits).'' \4\
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    \1\ 16 U.S.C. 824e.
    \2\ In this final rule, we use transmission provider to mean any 
public utility that owns, operates, or controls facilities used for 
the transmission of electric energy in interstate commerce. 18 CFR 
37.3 (2021). Therefore, unless otherwise noted, ``transmission 
provider'' refers only to public utility transmission providers. 
Furthermore, the term ``public utility'' as found in section 201(e) 
of the FPA means ``any person who owns or operates facilities 
subject to the jurisdiction of the Commission under this subchapter 
. . .'' 16 U.S.C. 824(e).
    \3\ The Commission's pro forma OATT defines Good Utility 
Practice as: ``[a]ny of the practices, methods and acts engaged in 
or approved by a significant portion of the electric utility 
industry during the relevant time period, or any of the practices, 
methods and acts which, in the exercise of reasonable judgment in 
light of the facts known at the time the decision was made, could 
have been expected to accomplish the desired result at a reasonable 
cost consistent with good business practices, reliability, safety 
and expedition. Good Utility Practice is not intended to be limited 
to the optimum practice, method, or act to the exclusion of all 
others, but rather to be acceptable practices, methods, or acts 
generally accepted in the region, including those practices required 
by Federal Power Act section 215(a)(4).'' Pro forma OATT section 
1.15.
    \4\ The definition also states, ``Relevant transmission 
equipment may include, but is not limited to, circuit breakers, line 
traps, and transformers.'' Managing Transmission Line Ratings, 
Notice of Proposed Rulemaking, 86 FR 6420 (Jan. 21, 2021), 173 FERC 
] 61,165, at P 85 (2020) (NOPR).
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    2. The transfer capability of a transmission line can change with 
ambient weather conditions. Thus, a transmission line rating can be 
determined by taking into consideration the physical characteristics of 
the conductor and making assumptions about ambient weather conditions 
to determine the maximum amount of power that can flow through a 
conductor while keeping the conductor under its maximum operating 
temperature. Conductor temperatures are impacted by a variety of 
factors,

[[Page 2245]]

including ambient air temperatures. Increases in ambient air 
temperatures tend to increase a transmission line's operating 
temperature and lower a transmission line's rating, while lower ambient 
air temperatures tend to lower a transmission line's operating 
temperature and increase the transmission line's rating.
    3. Many transmission line ratings are currently calculated based on 
assumptions about ambient conditions that are not regularly adjusted 
and therefore do not accurately reflect the near-term transfer 
capability of the transmission system.\5\ For example, when seasonal or 
static temperature assumptions exceed actual ambient air temperatures, 
transmission line ratings may understate the near-term transfer 
capability that the transmission system can actually provide, leading 
to unnecessarily restricted flows and potentially increased congestion 
costs. Alternatively, when ambient air temperatures exceed seasonal or 
static temperature assumptions, transmission line ratings may overstate 
the near-term transfer capability of the system, creating potential 
reliability and safety problems. In either case, the continued use of 
seasonal and static temperature assumptions may result in transmission 
line ratings that do not accurately represent the transfer capability 
of the transmission system. We find that transmission line ratings and 
the rules by which they are established are practices that directly 
affect the cost of wholesale energy, capacity, and ancillary services, 
as well as the cost of delivering wholesale energy to transmission 
customers; thus, we find that inaccurate transmission line ratings 
result in Commission-jurisdictional rates that are unjust and 
unreasonable.
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    \5\ Federal Energy Regulatory Commission, Staff Paper, Managing 
Transmission Line Ratings, Docket No. AD19-15-000 (Aug. 2019) 
(Commission Staff Paper), https://www.ferc.gov/sites/default/files/2020-05/tran-line-ratings.pdf.
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    4. To address these issues with respect to transmission service in 
the near term, we adopt, with certain modifications, the NOPR 
proposal's definition of an ambient-adjusted rating (AAR) as a 
transmission line rating that: (1) Applies to a time period of not 
greater than one hour; (2) reflects an up-to-date forecast of ambient 
air temperature across the time period to which the rating applies; (3) 
reflects the absence of solar heating during nighttime periods where 
the local sunrise/sunset times used to determine daytime and nighttime 
periods are updated at least monthly, if not more frequently; and (4) 
is calculated at least each hour, if not more frequently.\6\ 
Additionally, we adopt two requirements for greater use of AARs. First, 
we require that transmission providers--including RTOs/ISOs for 
transmission service at their seams \7\--use AARs as the basis for 
evaluation of transmission service requests that will end within 10 
days of the request. Second, we require that transmission providers--
including RTOs/ISOs for transmission service at their seams--use AARs 
as the basis for their determination of the necessity of certain 
curtailment, interruption, or redispatch of transmission service 
anticipated to occur within those 10 days.
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    \6\ 18 CFR 35.28(b)(10) (2021); Pro Forma OATT attach. M, AAR 
Definition.
    \7\ The term ``seam'' is commonly used by the industry to 
indicate the border between two transmission provider's service 
territories. Service at the seam can take different forms, such as 
point-to-point service or market-to-market service.
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    5. To address these issues with respect to transmission service in 
the longer term, we require that transmission providers use seasonal 
line ratings as the basis for evaluation of transmission service 
requests ending more than 10 days from the date of the request. We also 
require that transmission providers use seasonal line ratings as the 
basis for the determination of the necessity of curtailment, 
interruption, or redispatch of transmission service that is anticipated 
to occur more than 10 days in the future.\8\
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    \8\ The use of seasonal line ratings for long-term requests for 
transmission service and as the basis for the determination of 
curtailment, interruption, or redispatch is currently standard 
practice. However, as discussed below, we adopt certain reforms to 
change seasonal line rating implementation.
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    6. For both longer term and shorter term transmission service, we 
adopt exceptions to the AAR and seasonal line rating requirements to 
accommodate instances in which the transmission line rating of a 
transmission line is not affected by ambient air temperature and 
instances in which a transmission provider reasonably determines, 
consistent with good utility practice, that the use of a temporary 
alternate rating is necessary to ensure the safety and reliability of 
the transmission system.\9\
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    \9\ Because the new requirements related to AARs and seasonal 
line ratings are implemented through the new pro forma OATT 
Attachment M, these requirements are placed upon transmission 
providers. However, we recognize that transmission owners (not 
transmission providers) determine transmission line ratings. In many 
instances, the transmission provider and transmission owner are the 
same entity. However, below in Section IV.B.2.b, we discuss 
compliance within RTOs/ISOs, where the transmission provider and 
transmission owner are separate entities.
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    7. In certain situations, using transmission line ratings that are 
based on factors beyond forecasted ambient air temperatures and the 
presence or absence of solar heating may lead to greater accuracy. For 
example, the use of dynamic line ratings (DLRs) presents opportunities 
for transmission line ratings that may be more accurate than those 
established with AARs. Unlike AARs, DLRs are based not only on 
forecasted ambient air temperatures and the presence or absence of 
solar heating, but also on other weather conditions such as (but not 
limited to) wind, cloud cover, solar heating intensity (instead of mere 
daytime/nighttime distinctions used in AARs), and precipitation, and/or 
on transmission line conditions such as tension or sag. As discussed 
below, we adopt the NOPR's proposed definition of DLR as a transmission 
line rating that: (1) Applies to a time period of not greater than one 
hour; and (2) reflects up-to-date forecasts of inputs such as (but not 
limited to) ambient air temperature, wind, solar heating intensity, 
transmission line tension, or transmission line sag.
    8. Although some transmission owners have adopted the use of DLRs 
for individual transmission lines, there is not currently widespread 
use of DLRs. While DLRs can represent more accurate transmission line 
ratings than AARs, based on the record in this proceeding, we decline 
to mandate DLR implementation in this final rule. We instead 
incorporate the record in this proceeding on DLRs into new Docket No. 
AD22-5-000, which we open to further explore DLR implementation.
    9. One factor that may contribute to the limited deployment of DLRs 
by transmission owners is that the RTOs/ISOs that operate a large 
portion of the transmission system in the United States and oversee 
organized wholesale electric markets may not be able to automatically 
incorporate frequently updated transmission line ratings such as DLRs 
into their operating and market models. Although the record does not 
support a mandate for DLR implementation at this time, we require RTOs/
ISOs to establish and maintain the systems and procedures necessary to 
allow transmission owners in their regions to electronically update 
transmission line ratings on at least an hourly basis.
    10. In addition to reforms to improve the accuracy of transmission 
line ratings used during normal (pre-contingency) operations,\10\ we 
revise the pro forma

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OATT to require transmission providers to use uniquely determined 
emergency ratings for contingency analysis in the operations horizon 
and in post-contingency simulations of constraints.\11\ Such uniquely 
determined emergency ratings must also incorporate an adjustment for 
ambient air temperature and daytime/nighttime solar heating, consistent 
with our AAR requirements for normal ratings. Most transmission 
equipment can withstand high currents for short periods of time without 
sustaining damage. Emergency ratings reflect this technical capability, 
defining the specific additional current that a transmission line can 
withstand and for what duration the transmission line can withstand 
that additional current without sustaining damage. Because emergency 
ratings reflect this capability, uniquely determined emergency ratings 
will ensure more accurate transmission line ratings.
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    \10\ The North American Electric Reliability Corporation (NERC) 
Glossary defines ``normal rating'' as: ``[t]he rating as defined by 
the equipment owner that specifies the level of electrical loading . 
. . that a system, facility, or element can support or withstand 
through the daily demand cycles without loss of equipment life.'' 
NERC, Glossary of Terms Used in NERC Reliability Standards (June 28, 
2021), https://www.nerc.com/pa/Stand/Glossary%20of%20Terms/Glossary_of_Terms.pdf.
    \11\ As discussed below in Section IV.F.2.b, uniquely determined 
means the ratings are determined based on assumptions that reflect 
the specific, finite duration of emergency ratings, as opposed to 
using assumptions used to calculate normal ratings.
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    11. Finally, we adopt four requirements to enhance transparency. 
First, we require public utility transmission owners to share 
transmission line ratings and methodologies with their transmission 
provider(s) and with market monitors in RTOs/ISOs. Second, we require 
transmission providers to share their transmission owners' transmission 
line ratings and methodologies with any transmission provider(s) upon 
request. Third, we require transmission providers to maintain a 
database of their transmission owners' transmission line ratings and 
methodologies on the transmission provider's Open Access Same-Time 
Information System (OASIS) site or another password-protected website. 
Fourth, we require transmission providers to post on OASIS or another 
password-protected website any uses of exceptions or temporary 
alternate ratings. Availability of this additional information on 
transmission line ratings and their methodologies will facilitate more 
cost-effective decisions by transmission customers and more accurate 
transmission line ratings. We find that these transparency reforms will 
ensure that prices reflect the true cost of the wholesale service being 
provided and thereby are necessary to ensure just and reasonable 
wholesale rates.
    12. We require each transmission provider to submit a compliance 
filing within 120 days of the effective date of this final rule 
revising their OATT to incorporate pro forma OATT Attachment M. We 
further require that all requirements adopted herein be fully 
implemented no later than three years from the compliance filing due 
date.

II. Background

    13. In August 2019, Commission staff issued a paper entitled 
``Managing Transmission Line Ratings,'' which drew upon Commission 
staff outreach conducted in spring 2019 with RTOs/ISOs, transmission 
owners, and trade groups, as well as staff participation in a November 
2017 Idaho National Laboratory workshop. The report included background 
on common transmission line rating approaches, current practices in 
RTOs/ISOs, a review of pilot projects, and a discussion of potential 
improvements.\12\
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    \12\ Commission Staff Paper, https://www.ferc.gov/sites/default/files/2020-05/tran-line-ratings.pdf.
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    14. On September 10 and 11, 2019, Commission staff convened a 
technical conference (September 2019 Technical Conference) to discuss 
what transmission line ratings and related practices might constitute 
best practices, and what, if any, Commission action in these areas 
might be appropriate. In particular, the September 2019 Technical 
Conference covered issues such as: (1) Common transmission line rating 
methodologies; (2) AAR and DLR implementation benefits and challenges; 
(3) the ability of RTOs/ISOs to accept and use DLRs; and (4) the 
transparency of transmission line rating methodologies.\13\
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    \13\ Supplemental Notice of Technical Conference, Docket No. 
AD19-15-000 (Sep. 4, 2019).
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    15. In October 2019, the Commission requested comments on questions 
that arose from the September 2019 Technical Conference.\14\ In 
response, commenters addressed issues related to AARs and DLRs, 
emergency ratings, and transparency, as discussed below.
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    \14\ Notice Inviting Post-Technical Conference Comments, Docket 
No. AD19-15-000 (Oct. 2, 2019).
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    16. On November 19, 2020, the Commission issued the NOPR in this 
proceeding, proposing to amend the pro forma OATT and its regulations 
under the FPA to improve the accuracy and transparency of transmission 
line ratings.\15\ Specifically, the Commission proposed a new pro forma 
OATT Attachment M ``Transmission Line Ratings'' to require transmission 
providers to implement AARs on the transmission lines over which they 
provide transmission service. The Commission also proposed revisions to 
its regulations to require RTOs/ISOs to establish and implement the 
systems and procedures necessary to allow transmission owners to 
electronically update transmission line ratings at least hourly and to 
require transmission owners to share transmission line ratings and 
transmission line rating methodologies with their transmission 
provider(s) and, in RTOs/ISOs, with their market monitor(s). The 
Commission received comments from 56 entities on the NOPR proposals 
from a diverse set of stakeholders.\16\
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    \15\ Managing Transmission Line Ratings, Notice of Proposed 
Rulemaking, 86 FR 6420 (Jan. 21, 2021), 173 FERC ] 61,165 (2020) 
(NOPR).
    \16\ See Appendix A for a list of entities that submitted 
comments and the shortened names used throughout this final rule to 
describe those entities.
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III. Need for Reform

A. NOPR Proposal

    17. In the NOPR, the Commission preliminarily found that 
transmission line ratings and the rules by which they are established 
are practices that directly affect the cost of wholesale energy, 
capacity, and ancillary services, as well as the cost of delivering 
wholesale energy to transmission customers. The Commission explained 
that, because of the relationship between transmission line ratings and 
costs, inaccurate transmission line ratings may result in Commission-
jurisdictional rates that are unjust and unreasonable.\17\
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    \17\ NOPR, 173 FERC ] 61,165 at P 38.
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    18. The Commission explained that most transmission owners 
implement seasonal or static transmission line rating methodologies 
based on conservative, worst-case assumptions, such as high 
temperatures that are likely to occur over the longer term, but that 
often do not reflect the true near-term transfer capability of 
transmission facilities. Thus, the Commission reasoned, seasonal and 
static line ratings fail to reflect the true cost of delivering 
wholesale energy to transmission customers, and incorporating near-term 
forecasts of ambient air temperatures in transmission line ratings 
would more accurately reflect the actual cost of delivering wholesale 
energy to transmission customers.\18\
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    \18\ Id. P 39.
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    19. Because actual ambient air temperatures are usually not as high 
as the ambient air temperatures conservatively assumed in seasonal and 
static line ratings, the Commission

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observed that updating transmission line ratings used in near-term 
transmission service to reflect actual ambient air temperatures usually 
results in increased system transfer capability and, in turn, lower 
costs for consumers. However, the Commission also observed that 
seasonal and static line ratings can at times assume temperatures that 
are lower than the actual ambient air temperatures in the short term. 
In doing so, the Commission noted that seasonal or static transmission 
line rating methodologies can at times result in transmission line 
ratings that reflect more transfer capability than physically exists. 
The Commission observed that this overstatement of transmission line 
ratings similarly results in wholesale energy rates that fail to 
reflect the actual cost of delivering wholesale energy to transmission 
customers, and may also create reliability and safety problems, risk 
damage to equipment, and prevent occurrences of rates for scarcity 
pricing or transmission constraint penalty factors.\19\
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    \19\ Id. P 42.
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    20. Regarding DLR implementation, the Commission observed that some 
RTOs/ISOs may rely on software and systems that cannot accommodate 
transmission line ratings that frequently change, such as DLRs, and 
that, without reflecting such frequent changes to transmission line 
ratings, such software may serve as a barrier that prevents 
transmission owners in RTOs/ISOs from implementing DLRs, which can 
better reflect the actual transfer capability of the transmission 
system. The Commission explained that, in addition to ambient air 
temperature, DLRs incorporate additional inputs, including wind, cloud 
cover, solar heating, and precipitation, as well as transmission line 
conditions such as tension and sag. DLRs thereby provide transmission 
line ratings that are closer to the true thermal transmission line 
limit than AARs, which can result in rates that even more accurately 
reflect the costs of delivering wholesale energy to transmission 
customers than relying on AARs. However, the Commission explained that 
the potential inability of RTOs/ISOs to automatically accept and use 
DLRs provided by transmission owners may prevent RTO/ISO markets from 
benefiting from the more accurate representation of current RTO/ISO 
system conditions. In turn, by ensuring RTO/ISO market models can 
incorporate more accurate representations of system conditions when 
transmission owners use DLRs, RTO/ISO markets would produce prices that 
more accurately reflect the costs of delivering wholesale energy to 
transmission customers. For this reason, the Commission also 
preliminarily found in the NOPR that current transmission line rating 
practices in RTOs/ISOs that do not permit the acceptance of DLRs from 
transmission owners may result in rates that do not reflect the actual 
costs of delivering wholesale energy to transmission customers.\20\
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    \20\ Id. P 43.
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    21. Regarding emergency ratings, the Commission found that current 
transmission line rating practices may fail to use emergency ratings, 
and in failing to do so, may result in transmission line ratings that 
do not accurately reflect the near-term transfer capability of the 
system. This, in turn, may result in rates that do not reflect actual 
costs of delivering wholesale energy to transmission customers. In 
support, the Commission stated that transmission owners often develop 
two sets of transmission line ratings for most facilities: Normal 
ratings that can be safely used continuously, and emergency ratings 
that can be used for a specified shorter period of time, typically 
during post-contingency operations. Because emergency ratings are a 
more accurate representation of the flow limits over shorter 
timeframes, the Commission preliminarily found that their use in models 
of post-contingency flows may produce prices that more accurately 
reflect actual costs of delivering wholesale energy to transmission 
customers.\21\
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    \21\ Id. PP 44-46.
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    22. Finally, in the NOPR, the Commission preliminarily found that, 
by preventing transmission providers and, in RTO/ISOs, market monitors 
from having the opportunity to validate transmission line ratings in 
situations where a transmission provider serves any transmission owners 
that are not itself, current levels of transparency into transmission 
line ratings and transmission line rating methodologies may result in 
unjust and unreasonable rates. The Commission observed that a 
consequence of a lack of transparency could be inaccurate near-term 
transmission line ratings, which may result in rates that do not 
accurately reflect congestion and reserve costs on the system. As one 
example, the Commission stated that, without knowing the basis for a 
given transmission line rating that frequently binds and elevates 
prices, a transmission provider and/or market monitor cannot determine 
whether the transmission line rating is accurately calculated and 
therefore whether unjust and unreasonable wholesale rates are being 
created through use of inaccurate transmission line ratings.\22\
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    \22\ Id. P 47.
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B. Comments

    23. Commenters overwhelmingly agree with the Commission's 
preliminary finding that transmission line ratings and the rules by 
which they are established are practices that directly affect the cost 
of wholesale energy, capacity, and ancillary services, as well as the 
cost of delivering wholesale energy to transmission customers.\23\ 
Commenters also agree with the Commission's preliminary finding that, 
because of the relationship between transmission line ratings and 
wholesale energy costs, inaccurate transmission line ratings may result 
in Commission-jurisdictional rates that are unjust and 
unreasonable.\24\
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    \23\ AEP Comments at 3; Ohio FEA Comments at 6; New England 
State Agencies Comments at 8; OMS Comments at 6; Potomac Economics 
Comments at 5; CAISO DMM Comments at 4; SPP MMU Comments at 1-2; R 
Street Institute Comments at 2; Industrial Customer Organizations 
Comments at 11-12; TAPS Comments at 5-6; WATT Comments at 3-5; 
Certain TDU Comments at 4-5; Clean Energy Parties Comments at 2-3; 
EDFR Comments at 3.
    \24\ SPP MMU Comments at 1-2; Potomac Economics Comments at 5; 
CAISO DMM Comments at 4; Industrial Customer Organizations Comments 
at 11-12; TAPS Comments at 5-6; Certain TDU Comments at 4-5; Clean 
Energy Parties Comments at 2-3.
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    24. The majority of commenters representing state agencies support 
the Commission's basis for reform. New England State Agencies explain 
that, because transmission lines are used to control the amount of 
energy on electric power systems, transmission line ratings affect the 
price of electric power as well as the reliability of the electric 
grid.\25\ OMS also agrees with the Commission's preliminary finding 
that transmission line ratings directly affect wholesale energy costs 
and artificially limit transfers within and between regions, stating 
that such a conclusion is obvious and correct.\26\ OMS further contends 
that the slow pace of action on this issue by RTOs/ISOs and 
transmission owners makes the issue ripe for Commission action.\27\ 
Ohio FEA maintains that transmission line ratings have a direct and 
significant influence on wholesale energy and capacity markets and, 
therefore, must be accurate. Ohio FEA further argues that inaccurate 
transmission line ratings may also cause Locational Deliverability 
Areas (LDAs) to unnecessarily constrain in the

[[Page 2248]]

capacity market, resulting in higher capacity prices.\28\
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    \25\ New England State Agencies Comments at 8.
    \26\ OMS Comments at 6.
    \27\ OMS Reply Comments at 2-3.
    \28\ Ohio FEA Comments at 6.
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    25. Each of the commenting market monitors supports the 
Commission's basis for reform. For example, Potomac Economics agrees 
with the Commission's finding that inaccurate transmission line ratings 
may result in rates that are not just and reasonable and notes that 
facility ratings are used in virtually every aspect of electricity 
markets and system operations. Potomac Economics further avers that 
transmission line ratings determine the transmission limits input into 
market models, which, in turn, determine the commitment and dispatch 
needed to satisfy load and manage congestion. Potomac Economics further 
explains that underestimated transmission line ratings cause 
inefficient operations, higher congestion, reduced transmission 
availability, higher costs, higher renewable energy curtailments, and a 
greater perceived need for new transmission facilities.\29\ The SPP MMU 
also agrees with the Commission's assertion that transmission line 
ratings can directly affect the cost of producing wholesale energy, 
capacity, and ancillary services, as well as the cost of delivering 
such products. The SPP MMU explains that the cost of congestion is 
directly impacted by transmission line ratings and that inaccurate 
transmission line ratings cause price distortions, which may result in 
unjust and unreasonable rates.\30\ The CAISO DMM also agrees with the 
Commission's assessment that transmission line ratings and the rules by 
which they are established directly impact the cost of wholesale energy 
delivery and related services, explaining that static or seasonal line 
ratings can lead to increased costs when their assumptions are not 
realized, which may be inefficient and can result in excess cost paid 
by load.\31\
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    \29\ Potomac Economics Comments at 5.
    \30\ SPP MMU Comments at 1-2.
    \31\ CAISO DMM Comments at 4.
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    26. Other commenters also support the Commission's basis for 
reform. R Street Institute states that the Commission's problem 
statement is sound, explaining that transmission line ratings are 
chronically understated because they do not reflect current weather 
conditions, and as a result, according to R Street Institute, fail to 
allow for significant cost savings.\32\ Industrial Customer 
Organizations state that transmission line ratings and associated rules 
directly affect the cost of wholesale energy, capacity, and ancillary 
services, and the cost of delivering wholesale energy to transmission 
customers, and the rulemaking is therefore consistent with the 
Commission's authority and obligations under the FPA.\33\ TAPS states 
that reliance on static or seasonal line ratings inflicts unnecessary 
costs on consumers and that AAR deployment can provide significant 
benefits to consumers.\34\ WATT explains that accurate transmission 
line ratings lower costs for consumers.\35\ Certain TDUs assert that 
enhanced transmission line ratings, including AARs and DLRs, are tools 
that maximize the efficiency of the existing transmission system and 
lower costs for consumers.\36\
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    \32\ R Street Institute Comments at 2.
    \33\ Industrial Customer Organizations Comments at 11-12.
    \34\ TAPS Comments at 5-6.
    \35\ WATT Comments at 3-5.
    \36\ Certain TDUs Comments at 4.
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    27. Finally, clean energy and generator representatives also 
support the Commission's basis for reform.\37\ For example, Clean 
Energy Parties conclude that, due to the impact that transmission line 
ratings have on wholesale rates requirements, accurate transmission 
line ratings are consistent with the Commission's mandate under 
sections 205 and 206 of the FPA.\38\
---------------------------------------------------------------------------

    \37\ Clean Energy Parties Comments at 2-3; EDFR Comments at 3.
    \38\ Clean Energy Parties Comments at 2-3.
---------------------------------------------------------------------------

    28. However, NYTOs question the Commission's legal standing to 
regulate transmission line ratings, noting that the U.S. Court of 
Appeals for the District of Columbia Circuit (D.C. Circuit) found that 
there are limits to the Commission's FPA section 206 jurisdiction over 
``practices'' and that the term may not include all utility 
operations.\39\ NYTOs note that the Commission's authority to regulate 
transmission planning was upheld on appeal but that Order No. 1000 \40\ 
is not prescriptive; therefore, NYTOs request that the Commission 
similarly allow utilities to make their own decisions related to 
advanced line rating technologies.\41\
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    \39\ NYTOs Comments at 9 (referencing Cal. Indep. Sys. Operator 
Corp. v. FERC, 372 F.3d 395, 402 (D.C. Cir. 2004)).
    \40\ Transmission Planning and Cost Allocation by Transmission 
Owning and Operating Public Utilities, Order No. 1000, 77 FR 32184 
(May 31, 2012), 136 FERC ] 61,051 (2011), order on reh'g, Order No. 
1000-A, 139 FERC ] 61,132, order on reh'g and clarification, Order 
No. 1000-B, 141 FERC ] 61,044 (2012), aff'd sub nom. S.C. Pub. Serv. 
Auth. v. FERC, 762 F.3d 41 (D.C. Cir. 2014).
    \41\ NYTOs Comments at 9-10.
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C. Commission Determination

    29. We find that transmission line ratings, and the rules by which 
they are established, are practices that directly affect the rates for 
the transmission of electric energy in interstate commerce and the sale 
of electric energy at wholesale in interstate commerce (hereinafter 
referred to collectively as ``wholesale rates''). Thus, the Commission 
has jurisdiction over transmission line ratings.\42\ We further find 
that, because of the relationship between transmission line ratings and 
wholesale rates, inaccurate transmission line ratings result in 
wholesale rates that are unjust and unreasonable. Accordingly, pursuant 
to FPA section 206,\43\ we conclude that certain revisions to the pro 
forma OATT and the Commission's regulations are necessary to ensure 
just and reasonable wholesale rates. We adopt most of the reforms 
proposed in the NOPR, with certain clarifications, as discussed further 
herein, and revisions to the proposed pro forma OATT Attachment M and 
to the Commission's regulations.
---------------------------------------------------------------------------

    \42\ 16 U.S.C. 824(b)(1), 824d.
    \43\ 16 U.S.C. 824e.
---------------------------------------------------------------------------

    30. We find that transmission line ratings directly affect 
wholesale rates because transmission line ratings and wholesale rates 
are inextricably linked. As explained above, transmission line ratings 
represent the maximum transfer capability of each transmission line. 
That transfer capability determines the quantity of energy that can be 
transmitted from suppliers to load in any given moment. Supply and 
demand fundamentals dictate that less transfer capability (i.e., less 
supply) will result in higher rates, all else being equal. Inaccurate 
transmission line ratings can result in underutilization (or 
overutilization) of existing transmission facilities, thereby sending a 
signal that there is less (or more) transfer capability than is truly 
available. This signal impacts the wholesale rates charged for 
providing energy and other ancillary services. For example, if the 
system operator believes there is less transfer capability than is 
truly available, it may dispatch more expensive generators to serve 
load, when less expensive generators (which would have resulted in 
lower congestion costs) could have been used to reliably serve the same 
load. Alternatively, inaccurate transmission line ratings can result in 
oversubscription of existing transmission facilities, thereby sending 
the opposite signal--that there is more transfer capability than is 
truly available--which may risk damage to equipment, may fail to 
accurately price congestion costs, and may fail to signal to the market 
that more generation and/or transmission investment may be needed in 
the long term. We therefore find that transmission line ratings

[[Page 2249]]

directly affect wholesale rates and, concomitantly, that inaccurate 
transmission line ratings result in unjust and unreasonable wholesale 
rates.\44\
---------------------------------------------------------------------------

    \44\ SPP MMU Comments at 1-2; Potomac Economics Comments at 5; 
CAISO DMM Comments at 4; Industrial Customer Organizations Comments 
at 11-12; TAPS Comments at 5-6; Certain TDU Comments at 4-5; Clean 
Energy Parties Comments at 2-3.
---------------------------------------------------------------------------

    31. Most commenters, except NYTOs, agree with the Commission's 
preliminary conclusion that transmission line ratings directly affect 
wholesale rates.\45\ NYTOs caution that the D.C. Circuit found there 
are limits to the Commission's FPA section 206 jurisdiction over 
``practices'' and that the term may not include all utility 
operations.\46\ But, the inextricable link between transmission line 
ratings and wholesale rates places transmission line ratings within the 
Commission's FPA section 206 jurisdiction.
---------------------------------------------------------------------------

    \45\ AEP Comments at 3; Ohio FEA Comments at 6; New England 
State Agencies Comments at 8; OMS Comments at 6; Potomac Economics 
Comments at 5; CAISO DMM Comments at 4; SPP MMU Comments at 1-2; R 
Street Institute Comments at 2; Industrial Customer Organizations 
Comments at 11-12; TAPS Comments at 5-6; WATT Comments at 3-5; 
Certain TDU Comments at 4-5; Clean Energy Parties Comments at 2-3; 
EDFR Comments at 3.
    \46\ NYTOs Comments at 9-10.
---------------------------------------------------------------------------

    32. Some commenters, in response to the preliminary finding that 
accurate transmission line ratings are necessary for just and 
reasonable wholesale rates, argue that transmission line ratings are 
fundamentally a reliability tool.\47\ We agree that system safety and 
reliability are paramount to the proposed requirements for transmission 
line ratings. But we disagree with the suggestion that because 
transmission line ratings are critical to reliability, economic 
considerations are an inappropriate basis for requiring a certain type 
of transmission line ratings. Instead, we find that commenters present 
a false choice; economic considerations and reliability considerations 
are inextricably linked as reliability constraints bound the potential 
economic transactions of market participants. In the case of 
transmission line ratings, transmission owners calculate the maximum 
transfer capability of a transmission line. Transmission providers, in 
order to maintain reliable system operations, incorporate those ratings 
and other constraints into operations, and the results determine 
dispatch and commitment instructions and wholesale rates. Even though 
transmission line ratings can be seen as a reliability tool, that does 
not obviate the need to ensure that the wholesale rates resulting from 
such reliability tools are just and reasonable.
---------------------------------------------------------------------------

    \47\ See, e.g., Dominion Comments at 13; Exelon Comments at 6; 
PJM Indicated Transmission Owners Comments at 2; EEI Comments at 5.
---------------------------------------------------------------------------

    33. Regarding that incorporation of transmission line ratings into 
operations and resulting wholesale rates, as the Commission explained 
in the NOPR, most transmission owners implement seasonal or static line 
ratings. Such seasonal or static line ratings are based on 
conservative, worst-case assumptions about long-term conditions, such 
as the expected high temperatures that are likely to occur over the 
longer term. While such long-term assumptions may be appropriate in 
various planning contexts, they often do not reflect the true near-term 
transfer capability of transmission facilities and, when used in near-
term operations, produce unjust and unreasonable wholesale rates.
    34. As explained in the NOPR, incorporating near-term forecasts of 
ambient air temperatures in transmission line ratings can more 
accurately reflect the true near-term transfer capability of 
transmission facilities than continuing to rely on seasonal or static 
line ratings. Because actual ambient air temperatures are usually not 
as high as the ambient air temperatures conservatively assumed in 
seasonal and static line ratings, updating the transmission line 
ratings used in near-term transmission service to reflect actual 
ambient air temperatures usually results in increased system transfer 
capability. By increasing transfer capability, congestion costs will, 
on average, decline because transmission providers will be able to 
serve load with less expensive resources from what were previously 
constrained areas. For example, Potomac Economics has found that AAR 
implementation by those not already using AARs in MISO alone would have 
produced approximately $66.5 million and $49 million in reduced 
congestion costs in 2019 and in 2020, respectively.\48\ Such congestion 
cost changes and related overall price changes will more accurately 
reflect the actual congestion on the system, leading to wholesale rates 
that more accurately reflect the cost of the wholesale service being 
provided. Likewise, the ability to increase transmission flows into 
load pockets may reduce transmission provider reliance on local 
reserves inside load pockets, which may reduce local reserve 
requirements and the costs to maintain that required level of reserves.
---------------------------------------------------------------------------

    \48\ Potomac Economics Comments at 8.
---------------------------------------------------------------------------

    35. Moreover, while current transmission line rating practices 
usually understate transfer capability, they can also overstate 
transfer capability and, in doing so, place transmission lines at risk 
of inadvertent overload. While actual ambient air temperatures are 
usually not as high as the assumed seasonal or static line rating 
temperature input, in some instances actual ambient air temperatures 
exceed those assumed temperatures. In those instances, seasonal or 
static line ratings might reflect more transfer capability than 
physically exists, and therefore such transmission line ratings might 
allow access to some electric power supplies and/or demand that would 
not be available if transmission line ratings reflected the true 
transfer capability. Overstating transfer capability, like understating 
transfer capability, can result in wholesale rates that fail to reflect 
the cost of the wholesale service being provided, though, in the case 
of overstated transfer capability, through inaccurately low congestion 
pricing and failing to signal to the market that more generation and/or 
transmission investment may be needed in the long term.
    36. Regarding DLRs, in addition to ambient air temperatures and the 
presence or absence of solar heating, other weather conditions such as 
(but not limited to) wind, cloud cover, solar heating intensity, and 
precipitation, and transmission line conditions such as tension and 
sag, can affect the amount of transfer capability of a given 
transmission facility. DLRs incorporate these additional inputs and 
thereby provide transmission line ratings that are closer to the true 
thermal transmission line limits than AARs. However, as noted above and 
explained in greater detail in Section IV.E below, based on the record 
in this proceeding, we decline to mandate DLR implementation in this 
final rule. We instead incorporate the record in this proceeding on 
DLRs into new Docket No. AD22-5-000, which we open to further explore 
DLR implementation.
    37. While we believe additional record is needed regarding DLR 
implementation, we can determine based on the record that current 
transmission line rating practices in RTOs/ISOs that do not permit the 
acceptance of DLRs from transmission owners that use DLRs are 
contributing to unjust and unreasonable wholesale rates by acting as a 
barrier to accurate transmission line ratings. Therefore, as part of 
remedying inaccurate transmission line ratings that result in unjust 
and unreasonable wholesale rates, we require RTOs/ISOs to establish and 
maintain the systems and

[[Page 2250]]

procedures necessary to permit the acceptance of DLRs from transmission 
owners that use them. As the Commission explained in the NOPR, some 
RTOs/ISOs rely on software that cannot accommodate transmission line 
ratings that frequently change, such as DLRs.\49\ Without reflecting 
such frequent changes to transmission line ratings, such software 
serves as a barrier that prevents transmission owners in RTOs/ISOs from 
implementing DLRs and better reflecting the actual transfer capability 
of the transmission system. The result is that, even if a transmission 
owner sought to implement DLRs, the RTO's/ISO's energy management 
system (EMS) may not be able to accept and use the resulting 
transmission line rating. The potential inability of RTOs/ISOs to 
accept and use a DLR prevents RTO/ISO markets from benefiting from the 
more accurate representation of current system conditions. Therefore, 
we require RTOs/ISOs to establish and maintain the systems and 
procedures necessary to permit the acceptance of DLRs from transmission 
owners that use them.
---------------------------------------------------------------------------

    \49\ NOPR, 173 FERC ] 61,165 at P 43.
---------------------------------------------------------------------------

    38. Regarding emergency ratings, we find that many transmission 
owners' current transmission line rating practices fail to use 
emergency ratings, and in failing to do so, lead to transmission line 
ratings that do not accurately reflect the near-term transfer 
capability of the transmission system, and therefore result in 
wholesale rates that do not reflect costs of the wholesale service 
being provided. As the Commission explained in the NOPR, transmission 
owners often develop two sets of transmission line ratings for most 
facilities: Normal ratings that can be safely used continuously, and 
emergency ratings that can be used for a specified shorter period of 
time, typically during post-contingency operations. Transmission 
providers generally calculate resource dispatch and commitments to 
ensure that all facilities are within applicable facility ratings both 
during normal operations and following any modeled contingency (e.g., 
following the loss of a transmission line). In ensuring that the system 
is stable and reliable following a contingency, transmission providers 
often allow post-contingency flows on transmission lines to exceed 
normal ratings for short periods of time, as long as those flows do not 
exceed the applicable emergency rating for the corresponding timeframe. 
Because these emergency ratings are a more accurate representation of 
the flow limits over those shorter timeframes, their use in models of 
post-contingency flows produces wholesale rates that more accurately 
reflect the costs of the wholesale service being provided and therefore 
is necessary to ensure just and reasonable wholesale rates. For this 
reason, as described below, we require that transmission providers 
implement uniquely determined emergency ratings. Additionally, we 
require that transmission providers use uniquely determined emergency 
ratings for contingency analysis in the operations horizon and in post-
contingency simulations of constraints. Such uniquely determined 
emergency ratings must also include separate AAR calculations for each 
emergency rating duration used.
    39. Finally, we find that the current level of transparency into 
transmission line ratings and methodologies may result in unjust and 
unreasonable wholesale rates. In some regions, where the transmission 
owner and transmission provider are not the same entity, such as RTOs/
ISOs, current transparency levels prevent the transmission provider and 
market monitor(s) from having the opportunity to assess the accuracy of 
transmission line ratings. For example, as the Commission described in 
the NOPR, without knowing the basis for a given transmission line 
rating that frequently binds and elevates prices, a transmission 
provider and/or market monitor cannot determine whether the 
transmission line rating is accurately calculated.\50\ Moreover, we 
find that, absent additional information to market participants on 
transmission line ratings and their methodologies, the status quo does 
not provide market participants with information important to making 
cost-effective decisions and, thereby, impedes such decisions. For 
example, without accurate transmission line rating information, market 
participants operate without information that is important in making 
accurate economic decisions regarding where to build generation or 
where to site load. Further, this lack of transparency could allow 
transmission owners to submit inaccurate near-term transmission line 
ratings, which, in turn, would result in wholesale rates that do not 
accurately reflect the cost of the wholesale service being provided, as 
discussed above. For these reasons, we require: (1) Public utility 
transmission owners to share transmission line ratings and 
methodologies with their transmission provider(s) and with market 
monitors in RTOs/ISOs; (2) transmission providers to share their 
transmission owners' transmission line ratings and methodologies with 
any transmission provider(s) upon request; (3) transmission providers 
to maintain a database of their transmission owners' transmission line 
ratings and methodologies on the transmission provider's OASIS site or 
another password-protected website; and (4) transmission providers to 
post on OASIS or another password-protected website any uses of 
exceptions or temporary alternate ratings.
---------------------------------------------------------------------------

    \50\ Id. P 47.
---------------------------------------------------------------------------

IV. Discussion

A. Transmission Line Ratings Definition

1. NOPR Proposal
    40. In the NOPR, the Commission proposed to define a transmission 
line rating in pro forma OATT Attachment M as the maximum transfer 
capability of a transmission line, computed in accordance with a 
written transmission line rating methodology and consistent with good 
utility practice, considering the technical limitations on conductors 
and relevant transmission equipment (such as thermal flow limits), as 
well as technical limitations of the transmission system (such as 
system voltage and stability limits). Relevant transmission equipment 
may include, but is not limited to, circuit breakers, line traps, and 
transformers.\51\
---------------------------------------------------------------------------

    \51\ NOPR, 173 FERC ] 61,165 at P 85.
---------------------------------------------------------------------------

    41. Under the ``Obligations of Transmission Provider'' section in 
pro forma OATT Attachment M, the Commission further proposed to require 
that the transmission provider must use either AARs or seasonal line 
ratings, as appropriate, as the relevant transmission line ratings. 
Similarly, and as described in more detail in Section IV.D.3, the 
Commission proposed exceptions to the AAR and seasonal line rating 
requirements for certain transmission line ratings.
2. Comments
    42. Some commenters support the proposed definition of transmission 
line rating, while others request clarity or modifications be made, 
specifically around the list of relevant transmission equipment. AEP 
supports the Commission's proposed transmission line rating definition, 
explaining that the Commission's proposed definition reflects the fact 
that transmission line ratings incorporate a set of electrical 
equipment that collectively operate as a single bulk electric system 
element (e.g., transformers, relay protective devices, terminal 
equipment, and series and shunt compensation devices) and that the most 
limiting component from that

[[Page 2251]]

set determines the transmission line rating.\52\ Similarly, Indicated 
PJM Transmission Owners address the NOPR's proposed AAR requirements 
set forth in pro forma OATT Attachment M under ``Obligations of 
Transmission Provider'' (hereinafter referred to as ``the proposed AAR 
requirements'') as ambient-adjusted and seasonal line ratings, 
consistent with NERC's definition of facility rating,\53\ and describe 
Indicated PJM Transmission Owners' implementation of AARs, consistent 
with NERC's definition of facility ratings.\54\ PJM also describes the 
implementation of AARs for each of its transmission facilities.\55\
---------------------------------------------------------------------------

    \52\ AEP Comments at 2-3.
    \53\ The NERC Glossary defines a ``Facility Rating'' as: ``[t]he 
maximum or minimum voltage, current, frequency, or real or reactive 
power flow through a facility that does not violate the applicable 
equipment rating of any equipment comprising the facility.'' NERC, 
Glossary of Terms Used in NERC Reliability Standards (June 28, 
2021), https://www.nerc.com/pa/Stand/Glossary%20of%20Terms/Glossary_of_Terms.pdf.
    \54\ Indicated PJM Transmission Owners Comments at 1-2, 6-7.
    \55\ PJM Comments at 2-3.
---------------------------------------------------------------------------

    43. Entergy explains that overhead conductor ratings and ratings 
for ``ancillary equipment,'' or equipment that does not include a 
primary element, like conductors and transformers, can be temperature 
adjusted. According to Entergy, examples of ``ancillary equipment'' 
include breakers, switches, traps, busses, jumpers, current 
transformers, potential transformers, and relay equipment. Entergy 
further asserts, however, that shunt reactors, series capacitors, 
relays, current transformers, static VAR compensators, circuit 
breakers, autotransformers, copper weld (``CW'') buses, conductors, 
risers or jumpers, and, subject to limited exceptions, customer 
equipment have ratings that cannot be temperature adjusted.\56\ 
Eversource states that the ratings for relays and other equipment, such 
as splices, switches, and terminal equipment, are not impacted by 
ambient air temperatures.\57\ NYISO states that the majority of the 
bulk electric system equipment ratings in New York are able to be rated 
using AARs or DLRs,\58\ while NYTOs note that transmission line ratings 
may be based on non-conductor components which are not affected by 
ambient air temperatures.\59\ EEI and MISO Transmission Owners request 
clarity on the definition of transmission line rating and its specific 
applicability, stating that the AAR requirements should not apply to 
power transformers, but instead, under certain circumstances, to other 
types of transformers, including current transformers.\60\ EEI further 
explains that ratings for power transformers are generally the result 
of the efficiency of the heat transfer process, not ambient air 
temperatures directly, and thus requests that the Commission clarify 
that the references to transformers apply only to transformers that 
limit or impact transmission line ratings and not power transformers 
generally.\61\ Entergy similarly notes that transformer and relay 
ratings do not change with ambient conditions.\62\ ITC states that AARs 
cannot be applied to voltage or stability limits and therefore 
recommends that ``transmission line rating'' reflect the concepts of 
equipment and facility rating as defined by NERC in order to avoid 
confusion with a system operating limit.\63\ APS states that 
transmission lines with limitations associated with substation 
equipment or series capacitors, among other equipment in which the 
transmission line is not the limiting factor, may not experience 
changes to their transfer capabilities.\64\ MISO contends that the list 
could include potential relay trip limits and maximum power transfer 
limits.\65\
---------------------------------------------------------------------------

    \56\ Entergy Comments at 5-6.
    \57\ Eversource Comments at 3.
    \58\ NYISO Comments at 3-4.
    \59\ NYTOs Comments at 8.
    \60\ EEI Comments at 17-18; MISO Transmission Owners Comments at 
39-40.
    \61\ EEI Comments at 17-18.
    \62\ Entergy Comments at 9-10.
    \63\ ITC Comments at 11-12. The NERC Glossary defines an 
``Equipment Rating'' as: ``[t]he maximum and minimum voltage, 
current, frequency, real and reactive power flows on individual 
equipment under steady state, short-circuit and transient 
conditions, as permitted or assigned by the equipment owner.'' It 
defines a ``System Operating Limit'' as: ``[t]he value (such as MW, 
Mvar, amperes, frequency or volts) that satisfies the most limiting 
of the prescribed operating criteria for a specified system 
configuration to ensure operation within acceptable reliability 
criteria. System Operating Limits are based upon certain operating 
criteria. These include, but are not limited to: Facility Ratings 
(applicable pre- and post-Contingency Equipment Ratings or Facility 
Ratings); transient stability ratings (applicable pre- and post-
Contingency stability limits); voltage stability ratings (applicable 
pre- and post-Contingency voltage stability); and system voltage 
limits (applicable pre- and post-Contingency voltage limits).'' 
NERC, Glossary of Terms Used in NERC Reliability Standards (June 28, 
2021), https://www.nerc.com/pa/Stand/Glossary%20of%20Terms/Glossary_of_Terms.pdf.
    \64\ APS Comments at 3.
    \65\ MISO Comments at 34.
---------------------------------------------------------------------------

3. Commission Determination
    44. In this final rule, we adopt the definition of transmission 
line rating proposed in the NOPR. Specifically, we adopt the proposed 
definition that a transmission line rating means the maximum transfer 
capability of a transmission line, computed in accordance with a 
written transmission line rating methodology and consistent with good 
utility practice, considering the technical limitations on conductors 
and relevant transmission equipment (such as thermal flow limits), as 
well as technical limitations of the transmission system (such as 
system voltage and stability limits). Relevant transmission equipment 
may include, but is not limited to, circuit breakers, line traps, and 
transformers. As the Commission stated in the NOPR, system safety and 
reliability are paramount to the proposed requirements for transmission 
line ratings. We agree with AEP that the definition adopted herein 
reflects the fact that transmission line ratings must incorporate a set 
of electrical equipment ratings that collectively operate as a single 
bulk electric system element (e.g., transformers, relay protective 
devices, terminal equipment, and series and shunt compensation devices) 
and that the most limiting component from that set determines the 
transmission line rating.\66\
---------------------------------------------------------------------------

    \66\ AEP Comments at 2-3.
---------------------------------------------------------------------------

    45. In response to comments about the definition's inclusion of the 
technical limitations (such as thermal flow limits) on conductors and 
relevant transmission equipment, we clarify that the definition of 
transmission line rating encompasses transmission line ratings for 
electric system equipment that includes more than just overhead 
conductors. For example, it includes ratings for electric system 
equipment such as circuit breakers, line traps, and transformers. 
Additionally, as described in more detail below in Section IV.D.3, we 
adopt the list of proposed exceptions from the NOPR. Consequently, we 
do not require transmission line ratings that are not affected by 
ambient air temperatures to be rated using forecasts of ambient air 
temperatures. That said, we decline to define in this final rule which 
electric system equipment ratings are (or are not) affected by ambient 
air temperatures. Instead, we allow flexibility for individual 
transmission owners and transmission providers to apply good utility 
practice to determine which specific electric system equipment has 
ratings that are (or are not) affected by ambient air temperatures.
    46. Finally, in response to requests for clarification from EEI and 
MISO Transmission Owners regarding the applicability of the proposed 
AAR requirements to power transformers, we decline to provide a generic 
exception from the AAR requirement for power transformers. The 
operating limits of a power transformer are bounded by the

[[Page 2252]]

ambient air temperature, the average winding temperature, and the 
maximum winding hottest-spot temperature.\67\ However, we reiterate the 
exceptions adopted herein and discussed further below, which provide 
that any rating not affected by ambient air temperatures would not be 
required to incorporate forecasts of ambient air temperatures into the 
rating. Thus, if a transmission provider determines, consistent with 
good utility practice, that a specific power transformer's rating is 
not affected by ambient air temperature, then that power transformer 
would fall within the scope of such exceptions to the AAR requirement.
---------------------------------------------------------------------------

    \67\ Institute of Electrical and Electronics Engineers, IEEE 
Standard for General Requirements for Liquid-Immersed Distribution, 
Power, and Regulating Transformers, IEEE Std C57.91.00-2021.
---------------------------------------------------------------------------

B. Ambient-Adjusted Ratings

1. AAR Definition and Transmission Provider Obligations
a. NOPR Proposal
    47. In the NOPR, the Commission proposed to define an AAR in pro 
forma OATT Attachment M and in the Commission's regulations as a 
transmission line rating that: (1) Applies to a time period of not 
greater than one hour; (2) reflects an up-to-date forecast of ambient 
air temperature across the time period to which the rating applies; and 
(3) is calculated at least each hour, if not more frequently. As 
obligations of the transmission provider set forth in pro forma OATT 
Attachment M, the Commission proposed to require that transmission 
providers use AARs as the applicable line rating: (1) For requests for 
near-term point-to-point transmission service ending within 10 days of 
the request date, as defined in pro forma OATT Attachment M; (2) for 
determining the necessity of near-term curtailment or interruption of 
near-term point-to-point transmission service anticipated to occur 
(start and end) within the next 10 days; and (3) for determining the 
necessity of near-term interruption or redispatch of network 
transmission service anticipated to occur (start and end) within the 
next 10 days. The Commission proposed to require transmission providers 
to implement the use of AARs and seasonal line ratings on all 
historically congested transmission lines \68\ within one year after 
the compliance filing due date and on all other transmission lines 
within two years after the compliance filing due date.\69\ For RTOs/
ISOs, for which the Commission has approved variations from the pro 
forma OATT to manage congestion and initiate curtailments and/or 
redispatch of transmission service within their footprints (although 
generally not at their borders), the Commission proposed two 
requirements. First, the Commission proposed requirements for RTOs/ISOs 
to implement AARs in both the day-ahead and real-time markets and any 
intra-day reliability unit commitment. Second, the Commission proposed 
to require AARs as the relevant transmission line rating for any near-
term point-to-point transmission service offered (e.g., at the RTO's/
ISO's borders).
---------------------------------------------------------------------------

    \68\ The Commission proposed to define a historically congested 
transmission line as ``a transmission line that was congested at any 
time in the five years prior to the effective date of [this final 
rule].'' NOPR, 173 FERC ] 61,165 at P 92.
    \69\ Id. P 131.
---------------------------------------------------------------------------

    48. As justification for the NOPR proposal to require AAR 
implementation on all transmission lines and not only on historically 
congested lines, the Commission noted that any facility can become the 
most limiting element as the transmission system changes, and in 
certain circumstances flows may change considerably from normal 
operations. Therefore, the Commission proposed to require AARs be 
implemented on all transmission lines but recognized that a staggered 
implementation schedule would allow transmission providers and 
transmission owners to focus initial implementation where it would have 
the most impact.\70\
---------------------------------------------------------------------------

    \70\ Id. PP 93-94.
---------------------------------------------------------------------------

    49. As justification for requiring AARs, the Commission 
preliminarily found that AAR requirements strike an appropriate balance 
between benefits and challenges. First, the Commission observed that, 
while there are differences across transmission systems, simply 
accounting for ambient air temperatures in transmission line ratings 
can reliably increase power transfer capability and significantly lower 
production costs at a manageable implementation cost. The Commission 
next explained that, according to Potomac Economics' estimates, the 
benefits to AAR implementation by those not already implementing AARs 
in MISO alone would have produced approximately $94 million and $78 
million in reduced congestion costs in 2017 and in 2018, respectively. 
The Commission further explained that, while several entities noted 
implementation costs as a barrier to AAR implementation, the costs 
identified were mostly initial investments in upgraded OASIS and/or EMS 
and ratings databases and that once these systems are upgraded, adding 
AARs to additional transmission lines appears to have a minimal 
incremental cost.\71\
---------------------------------------------------------------------------

    \71\ Id. P 99.
---------------------------------------------------------------------------

b. Comments
    50. In response to the proposed AAR requirements, RTO/ISO comments 
are mixed, with most requesting flexibility to accommodate regional or 
market differences,\72\ while market monitors are generally supportive 
of the NOPR proposal.\73\ Transmission owners are conceptually 
supportive of AAR implementation but request flexibility in response to 
what they generally describe as an overly broad requirement.\74\ The 
PJM transmission owners that submitted comments are generally 
supportive of the proposed AAR requirements in pro forma OATT 
Attachment M, explaining that they have experience using AARs.\75\ 
Other commenters, including state governments, generation, load, 
renewable energy advocates, and other technical experts, are generally 
supportive of the proposed AAR requirements.\76\
---------------------------------------------------------------------------

    \72\ See, e.g., MISO Comments at 7, 9, 14-16; NYISO Comments at 
9-11; ISO-NE Comments at 9.
    \73\ Potomac Economics Comments at 3-4; CAISO DMM Comments at 2-
4; SPP MMU Comments at 1, 4.
    \74\ MISO Transmission Owners Comments at 8-9; PacifiCorp 
Comments at 2; EEI Comments at 2-5; NRECA/LPPC Comments at 2-3; 
Entergy Comments at 1-2; BPA Comments at 2-4; WAPA Comments at 4-5; 
APS Comments at 2-4; Southern Company Comments at 2-3; NYTOs 
Comments at 2-3; Duke Energy Comments at 1-2; PG&E Comments at 3; 
SCE Comments at 1-2; SDG&E Comments at 1-2; LADWP Comments at 2-3; 
IID Comments at 4-6; ITC Comments at 1-3; Sunflower Comments at 2; 
Eversource Comments at 5-7.
    \75\ Exelon Comments at 1-2; AEP Comments at 5-6; Dominion 
Comments at 3-4; Indicated PJM Transmission Owner Comments at 1-4.
    \76\ New England State Agencies Comments at 10; OMS Comments at 
2; Ohio FEA Comments at 2; R Street Institute Comments at 1-2; WATT 
Comments at 1-2; DC Energy Comments at 1-2; ACORE Comments at 1; 
Clean Energy Parties Comments at 2, 4-6; ENEL Comments at 1; EDFR 
Comments at 1-2; Vistra Comments at 1-2; EPSA Comments at 2; 
Industrial Customers Comments at 1-2; TAPS Comments at 1-2; Certain 
TDU Comments at 1.
---------------------------------------------------------------------------

    51. Several transmission owners explain that they currently use 
AARs on all or parts of their transmission lines and support the 
Commission's NOPR proposal to implement widespread AAR use. AEP notes 
that it has used AARs in real-time operations for decades and that AARs 
have provided both reliability and financial benefits.\77\ AEP notes 
that the use of AARs is common in PJM and that it similarly implements 
AARs for its facilities in SPP and the Electric Reliability Council of 
Texas (ERCOT).\78\ Exelon states that it

[[Page 2253]]

considers AARs to be a best practice, explaining that all of its six 
utilities have implemented AARs on their transmission systems, without 
any adverse reliability or safety impacts, and have found the practice 
to be a cost-effective tool to enhance grid reliability.\79\ Dominion 
states that, because PJM has implemented AARs for transmission service 
and for use in its day-ahead and real-time markets, Dominion Energy 
Virginia has adopted and uses PJM's AAR methodology on all its 
transmission lines, while Dominion Energy South Carolina uses AARs on 
only a portion of its transmission system.\80\ Indicated PJM 
Transmission Owners support efforts to enhance transmission utilization 
by requiring AAR and seasonal line rating implementation, explaining 
that such practices improve efficiency; they also state that 
transmission line ratings are fundamentally a reliability tool.\81\ 
While generally supportive of the NOPR proposal, Dominion, AEP, and 
Indicated PJM Transmission Owners all request flexibility to 
accommodate PJM's current AAR implementation and ask that the 
Commission not require hourly updates to AARs.\82\
---------------------------------------------------------------------------

    \77\ AEP Comments at 3.
    \78\ Id. at 3-4.
    \79\ Exelon Comments at 1-2.
    \80\ Dominion Comments at 6.
    \81\ Indicated PJM Transmission Owners Comments at 1-2.
    \82\ Dominion Comments at 3; AEP Comments at 6-7; Indicated PJM 
Transmission Owners Comments at 5.
---------------------------------------------------------------------------

    52. Both ITC and Sunflower state that they are generally supportive 
of AAR implementation, but urge flexibility for transmission providers 
to implement AARs.\83\ MISO Transmission Owners, explaining that they 
have initiated a process to implement AARs, state that they support 
certain aspects of the NOPR, but also state that other aspects are 
overly broad and will not yield sufficient benefits to justify the 
costs.\84\ MISO Transmission Owners urge the Commission to allow for 
regional flexibility in any requirements and state that AAR deployment 
should focus on where it is expected to provide benefits by ``freeing 
up'' additional transfer capability.\85\ MISO Transmission Owners state 
that, over the past five years, congestion arose on only 10% of the 
nearly 10,000 transmission facilities under MISO's functional control 
and that there would be no benefit to implementing AARs on non-
congested lines.\86\ MISO Transmission Owners also state that there are 
several necessary steps to implement AARs, which can be costly and time 
consuming.\87\ Additionally, MISO Transmission Owners state that the 
Commission should not rely upon Potomac Economics' estimates of AAR 
benefits, explaining that Potomac Economics inaccurately assumed that: 
(1) All transmission lines are ambient adjustable; (2) all transmission 
owners are using worst-case assumptions; and (3) congestion caused by 
transient outages existed even though it has since been alleviated by 
recent upgrades.\88\
---------------------------------------------------------------------------

    \83\ ITC Comments at 1-3; Sunflower Comments at 2.
    \84\ MISO Transmission Owners Comments at 3-4.
    \85\ Id. at 13.
    \86\ Id. at 28.
    \87\ Id. at 22.
    \88\ Id. at 43-45.
---------------------------------------------------------------------------

    53. NYTOs, Eversource, and Southern Company request that the 
Commission refrain from adopting blanket AAR requirements for all 
transmission lines and instead require transmission providers to adopt 
a process for determining whether to apply AARs or DLRs to certain 
transmission facilities.\89\ Southern Company suggests that such a 
process could be similar to the Commission's available transfer 
capability (ATC) requirements, whereby a public utility could include 
the metrics and criteria for determining when to use AAR or DLR in its 
OATT and implementation details in its guidelines or business 
practices.\90\ Southern Company states that, while broader use of AARs 
and DLRs may provide cost savings to customers, the Commission's 
proposed approach in the NOPR is overly prescriptive and may therefore 
create unnecessary implementation complications and limit the 
deployment of other grid-enhancing technologies.\91\ Southern Company 
and NRECA/LPPC also argue that non-RTO/ISO regions are characterized by 
long-term transmission commitments and that incremental short-term 
transfer capability is less relevant and less likely to result in cost 
savings.\92\ Eversource contends that it applies AARs where it is 
beneficial, but states that the benefits of AARs will depend on 
specific circumstances within a region, noting that there is little 
congestion in ISO-NE.\93\
---------------------------------------------------------------------------

    \89\ Southern Company Comments at 1-2; Eversource Comments at 6; 
NYTOs Comments at 10.
    \90\ Southern Company Comments at 1-2.
    \91\ Id. at 2.
    \92\ Id. at 4-5; NRECA/LPPC Comments at 19.
    \93\ Eversource Comments at 4-5.
---------------------------------------------------------------------------

    54. Southern Company states that reliability issues may arise as a 
result of the NOPR proposal because AARs may create difficulties in 
identifying the most limiting element, which may change as the 
temperature changes, and similar difficulties may arise in complying 
with Reliability Standard PRC-023-4's transmission relay loadability 
requirements that depend on maximum published ratings.\94\ EEI states 
that, to ensure compliance with Reliability Standard PRC-023-4, 
significant amounts of field engineering time could be required to 
install and test new settings for thousands of relays.\95\ NYTOs state 
that implementing the AAR requirements will require significant time 
and resources and would divert scarce resources from ongoing efforts to 
meet the goals of New York's Climate Leadership and Community 
Protection Act.\96\ NERC contends that the Commission should keep in 
mind considerations for implementing AARs across long transmission 
lines that span multiple climates.\97\
---------------------------------------------------------------------------

    \94\ Southern Company Comments at 6.
    \95\ EEI Comments at 5-6.
    \96\ NYTOs Comments at 6-7.
    \97\ NERC Comments at 7.
---------------------------------------------------------------------------

    55. Duke Energy states that it already employs AARs in real-time 
operations and supports the Commission's proposed requirements for 
transmission providers to implement AARs in real-time operations.\98\ 
However, Duke Energy also argues that, because incorporating AARs into 
ATC calculations would require fundamental software changes that may 
take several million dollars and multiple years to complete, the 
benefits may not outweigh the costs.\99\ Duke Energy suggests that the 
Commission should instead require transmission providers to submit a 
compliance filing in which they may propose a process to identify the 
transmission facilities for which the implementation of AARs and 
seasonal line ratings will provide the most benefits to customers.\100\
---------------------------------------------------------------------------

    \98\ Duke Energy Comments at 5.
    \99\ Id. at 10.
    \100\ Id. at 5.
---------------------------------------------------------------------------

    56. EEI states that its experience with AARs is that their use can 
provide benefits on a subset of transmission lines \101\ and requests 
flexibility for transmission owners and transmission providers to 
implement transmission line rating solutions that best suit their 
needs.\102\ EEI recommends a staggered AAR approach whereby AARs would 
first be implemented on priority designated facilities, using 
established and studied criteria, and any subsequent AAR implementation 
would occur following further studies of potential benefits.\103\ 
Similarly, Entergy states that AARs allow for more flexibility in real-
time operations than static/thermal values for real-time contingency 
studies,

[[Page 2254]]

but contends that the use of AARs should follow a scientific 
application of factors that can reasonably result in an adjustment of 
facility ratings to those facilities for which an adjustment would be 
reasonably expected to provide benefits that exceed costs.\104\
---------------------------------------------------------------------------

    \101\ EEI Comments at 5.
    \102\ Id. at 2-4.
    \103\ Id.
    \104\ Entergy Comments at 8.
---------------------------------------------------------------------------

    57. NRECA/LPPC, Sunflower, and WAPA contend that the promised 
benefits, costs, and risks of AARs are not evenly distributed 
nationwide and that blanket application of the proposed AAR 
requirements poses difficult operating challenges.\105\ NRECA/LPPC 
argue that the Commission should maintain a focus on safety and 
reliability and limit the scope of any final rule by applying the AAR 
requirements to transmission lines: (1) Rated 100 kV and above; (2) 
that are historically congested due to conductor limitations only; and 
(3) that are under RTO/ISO control. In addition, NRECA/LPPC argue that 
AAR requirements should be limited to transmission service used for 
near-term wholesale transactions, which in the RTOs/ISOs would be the 
day-head and real-time markets, and outside of the RTOs/ISOs, if 
applied, would be daily and hourly ATC, curtailment, and 
redispatch.\106\ NRECA/LPPC and Sunflower further contend that, due to 
challenges in implementing AARs, utilities should have the flexibility 
to choose the AAR methodology best suited to their needs and should 
provide a waiver mechanism for particular circuits on which AAR 
implementation is difficult.\107\
---------------------------------------------------------------------------

    \105\ NRECA/LPPC Comments at 15-16, 19; Sunflower Comments at 5; 
WAPA Comments at 5.
    \106\ NRECA/LPPC Comments at 2-3.
    \107\ Id. at 3; Sunflower Comments at 5.
---------------------------------------------------------------------------

    58. Several Western Interconnection, non-CAISO transmission owners, 
including PacifiCorp, BPA, WAPA, and APS, broadly support the adoption 
of AARs due to the associated reduction in congestion, increase in 
transfer capability, and reliability improvements. However, these 
transmission owners request additional flexibility in how transmission 
owners apply AARs and urge the Commission to not adopt blanket AAR 
requirements for all transmission lines given differences in terrain, 
line lengths, and scarcity of temperature data for such lines.\108\ In 
explaining the drawbacks to blanket AAR implementation, APS explains 
that non-congested transmission lines, transmission lines that are 
substation equipment-limited, and transmission lines that are voltage- 
and stability-limited will not benefit from AAR implementation.\109\ 
WAPA further identifies additional AAR implementation challenges, 
including the installation of new devices, communication equipment, and 
cybersecurity challenges. To reduce implementation burdens, WAPA 
recommends that the Commission examine real-time Total Transfer 
Capability (TTC) calculations.\110\ WAPA further cautions that it would 
have to pass the costs of AAR implementation on to all customers, even 
though only some customers would benefit.\111\ BPA states that if it 
uses AARs as proposed, it would need to make its wind assumptions more 
conservative, de-rating transmission, to mitigate the risk of operating 
near the conductor limit.\112\
---------------------------------------------------------------------------

    \108\ PacifiCorp Comments at 2; BPA Comments at 2-4; WAPA 
Comments at 4-5; APS Comments at 2-4.
    \109\ APS Comments at 2-4.
    \110\ WAPA Comments at 7-9.
    \111\ Id. at 4-5.
    \112\ BPA Comments at 4-5.
---------------------------------------------------------------------------

    59. PacifiCorp, BPA, EEI, and IID further explain additional 
difficulties they would face implementing the proposed requirements to 
incorporate AARs into ATC that could render AAR implementation 
infeasible.\113\ IID explains that, in the Western Interconnection, 
path limits are the result of multiple limits in series and in 
parallel. TTC calculations involve adjusting a base case with an 
associated series of activities, and failures in base case studies have 
to be evaluated manually, such that a generic equation would be 
insufficient in calculating transmission line ratings.\114\ BPA and 
PacifiCorp explain that most congested parts on their transmission 
systems are lines that are operated in parallel as part of a rated 
transmission path,\115\ that such rated paths have interactions with 
other paths, which result in operating nomograms,\116\ and that the 
NOPR proposal may be more appropriate for a flow-based transmission 
system.\117\ According to PacifiCorp and BPA, it may be infeasible to 
implement AARs as it would substantially increase the time to compute 
the constraints that they use to calculate TTC.\118\ CAISO also 
describes the TTC calculation process using rated paths and states that 
using hourly AARs would exponentially increase the complexity of such 
calculations and would necessitate further automation.\119\ Similarly 
describing the challenges of incorporating AARs into ATC, EEI explains 
that, in some areas, TTC values are determined annually, or even less 
frequently.\120\
---------------------------------------------------------------------------

    \113\ Id. at 3-4; PacifiCorp Comments at 2; IID Comments at 5-6; 
EEI Comments at 10-11.
    \114\ IID Comments at 5.
    \115\ BPA Comments at 3; PacifiCorp Comments at 2.
    \116\ Nomograms are operating constraints related to the flow on 
multiple paths that generally result from the simultaneous 
interaction between those paths.
    \117\ BPA Comments at 3; PacifiCorp Comments at 2.
    \118\ BPA Comments at 3; PacifiCorp Comments at 2.
    \119\ CAISO Comments at 10.
    \120\ EEI Comments at 11.
---------------------------------------------------------------------------

    60. California transmission owners urge more targeted AAR 
implementation.\121\ PG&E recommends requiring transmission owners to 
determine which lines would realize net benefits for customers if AARs 
were deployed, noting that deployment of AARs across all transmission 
lines could result in a negative return on investment and an increased 
risk profile for the transmission system.\122\ PG&E notes that most of 
its weather stations are currently located in ``High Fire Threat 
Districts'' and contends that AAR implementation on 500 kV lines will 
require planning for additional weather station equipment to ensure 
that accurate weather data is available.\123\ SCE advocates for phased 
AAR implementation in which transmission owners identify priority 
facilities, and, after implementation, study their implementation in a 
report filed with the Commission.\124\ SDG&E contends that settings for 
all relays will have to be studied and installed in the field, causing 
a significant cost burden unaccounted for in the Commission's 
analysis.\125\ IID contends that the Commission should not take a one-
size-fits-all approach and, in addition to the challenges of AAR 
implementation, encourages the Commission to consider the costs of 
software, equipment, and staffing in comparison to the benefits of AARs 
providing congestion relief.\126\
---------------------------------------------------------------------------

    \121\ PG&E Comments at 3; SCE Comments at 1-2; SDG&E Comments at 
1-2; LADWP Comments at 2-3.
    \122\ PG&E Comments at 3.
    \123\ Id. at 9-10.
    \124\ SCE Comments at 3-4.
    \125\ SDG&E Comments at 4.
    \126\ IID Comments at 5.
---------------------------------------------------------------------------

    61. LADWP states that Southern California loads peak in the summer 
when temperatures are already high and may not allow AARs to expand 
transfer capability. Conversely, according to LADWP, there is already 
abundant transfer capability in the winter months.\127\ Describing AAR 
implementation challenges, LADWP notes that, due to the diversity in 
terrain and microclimates that western transmission lines traverse, 
weather forecasts can vary significantly during volatile weather 
seasons and present

[[Page 2255]]

challenges in identifying the most constraining ambient conditions for 
a given transmission line.\128\ LADWP therefore contends that the 
Commission should consider offering regional exceptions from the AAR 
requirements or prescribing AARs only in areas where significant 
benefits are expected.\129\
---------------------------------------------------------------------------

    \127\ LADWP Comments at 3-4.
    \128\ Id. at 5-6.
    \129\ Id. at 4-5.
---------------------------------------------------------------------------

    62. PJM generally supports the adoption of AARs by transmission 
providers. PJM states that it already employs AARs in its operations 
and day-ahead and real-time markets and that the use of AARs is 
commonplace among the overwhelming majority of transmission owners in 
the PJM region. PJM states that transmission owners' utilization of 
AARs increases operational flexibility, promotes a more efficient use 
of the transmission system, and results in more reliable system 
dispatch and cost-effective market operations.\130\
---------------------------------------------------------------------------

    \130\ PJM Comments at 2.
---------------------------------------------------------------------------

    63. CAISO states that it currently uses seasonal line ratings, 
emergency ratings, and AARs. However, CAISO notes that AARs are used on 
relatively few facilities and involve a manual process to update 
transmission line ratings for an applicable period. CAISO states that, 
while AARs provide a more accurate understanding of the transfer 
capability of the transmission system, CAISO recommends that the 
Commission allow transmission owners and transmission providers to 
justify when they use AARs.\131\
---------------------------------------------------------------------------

    \131\ CAISO Comments at 2.
---------------------------------------------------------------------------

    64. MISO states that AAR and DLR deployment can support the 
efficient use of existing transmission infrastructure but is not a 
long-term solution to meet emerging system needs. MISO states that the 
Commission should not mandate the use of AARs where the burden of that 
deployment is greater than the benefits to be expected. MISO contends 
that the Commission should explore options for a more targeted 
application of identifying facilities that are good candidates for AARs 
based on objective criteria and documented methodologies.\132\ MISO 
notes that it and MISO Transmission Owners have already commenced an 
effort to identify a prioritized list of candidate transmission 
facilities for deployment of real-time AARs in MISO.\133\
---------------------------------------------------------------------------

    \132\ MISO Comments at 9.
    \133\ MISO Comments at 14.
---------------------------------------------------------------------------

    65. NYISO does not support a uniform approach to managing 
transmission line ratings and instead requests that each RTO/ISO work 
with the Commission to set objectives for its markets.\134\ NYISO 
contends that AAR use would not provide benefits everywhere.\135\ NYISO 
explains that using AARs to modify day-ahead transmission line ratings 
would overly complicate the day-ahead market solution and would reduce 
efficiency.\136\ NYISO requests flexibility for regional variation with 
transmission line ratings given regional differences, such as 
transmission scheduling and market rules.\137\ NYISO states that it 
could work with stakeholders to develop a proposal to implement three 
to four sets of seasonal line ratings that would be easier to implement 
and still achieve many of the NOPR objectives.\138\
---------------------------------------------------------------------------

    \134\ NYISO Comments at 1.
    \135\ Id. at 2.
    \136\ Id. at 1-2.
    \137\ Id. at 2.
    \138\ Id. at 20.
---------------------------------------------------------------------------

    66. Neither ISO-NE nor SPP explicitly takes a position on the NOPR 
proposal to implement AARs. However, ISO-NE states that most of the 
congestion that occurs on its system is due to voltage or stability 
limitations, and thus AAR benefits may be limited.\139\ ISO-NE 
estimates that the implementation of AARs could result in the lowering 
of thermal congestion costs by, at most, approximately $5-10 million 
per year.\140\ ISO-NE also contends, however, that AAR implementation 
may expose other binding system limitations without appreciably 
increasing transfer capability or reducing congestion.\141\
---------------------------------------------------------------------------

    \139\ ISO-NE Comments at 4-6.
    \140\ Id. at 5 (basing estimates on 2019 data contained in IMM 
and EMM Reports and the Commission's estimates of potential savings 
from AARs in other RTO/ISO regions).
    \141\ Id. at 6.
---------------------------------------------------------------------------

    67. Market monitors are mostly supportive of the proposed AAR 
requirements.\142\ The SPP MMU supports the proposed reforms to improve 
the accuracy and transparency of transmission line ratings used by 
transmission providers. The SPP MMU notes that numerous SPP 
transmission lines are not rated according to SPP Planning 
Criteria.\143\ The SPP MMU states that it supports the use of DLRs for 
all transmission lines.\144\ According to the SPP MMU, when 
transmission line ratings underestimate the actual transfer capability 
of the transmission system, this can result in restricted flows on 
certain paths while overloading others and can create a potential for 
de facto physical withholding of the available transfer capability by 
transmission owners.\145\ The SPP MMU argues that more accurate 
transmission line ratings will improve the robustness of price 
formation, particularly in congested areas.\146\
---------------------------------------------------------------------------

    \142\ Potomac Economics Comments at 3-4; CAISO DMM Comments at 
2-4; SPP MMU Comments at 1, 4.
    \143\ SPP MMU Comments at 4.
    \144\ Id. at 1, 4.
    \145\ Id. at 7.
    \146\ Id. at 9.
---------------------------------------------------------------------------

    68. Potomac Economics states that only 8% of the transmission line 
ratings in MISO are adjusted for changes in ambient air temperatures. 
Potomac Economics indicates that it conservatively estimates that the 
benefits of using AARs and emergency ratings in 2019 and 2020 would 
have been between 9% and 13% of the real-time congestion value, or $98 
million and $114 million per year.\147\ Potomac Economics notes that 
transmission owners have little or no economic incentive to provide 
temperature-adjusted ratings and that transmission operators \148\ 
rarely verify or validate transmission line rating methodologies or 
transmission line rating calculations.\149\ Potomac Economics contends 
that it would be unreasonable to require AARs on all transmission 
facilities, and instead argues that it would be more reasonable to 
require that processes be established to allow for additional AARs to 
be deployed quickly when new constraints begin to bind or other studies 
indicate it may be appropriate.\150\ Potomac Economics cautions, 
however, against requiring any cost-benefit analysis, noting that the 
incremental cost of initiating AARs on new constraints is near zero so 
such analysis is unnecessary.\151\ Finally, Potomac Economics contends 
that using AARs and emergency ratings will not create reliability 
concerns as the NOPR proposal only requires that decisions to not 
implement AARs or emergency ratings be based on reliability and not a 
preference or policy decision.\152\ CAISO DMM supports the proposed 
requirements to implement hourly AARs as a way to improve both the 
accuracy of congestion costs and transmission system efficiency.\153\
---------------------------------------------------------------------------

    \147\ Potomac Economics Comments at 7-9; see also Potomac 
Economics Reply Comments at 2-6.
    \148\ The NERC Glossary defines a ``Transmission Operator'' as: 
``[t]he entity responsible for the reliability of its `local' 
transmission system, and that operates or directs the operations of 
the transmission Facilities.'' NERC, Glossary of Terms Used in NERC 
Reliability Standards (June 28, 2021), https://www.nerc.com/pa/Stand/Glossary%20of%20Terms/Glossary_of_Terms.pdf.
    \149\ Potomac Economics Comments at 9-10; see also Potomac 
Economics Reply Comments at 6-7.
    \150\ Potomac Economics Comments at 20; see also Potomac 
Economics Reply Comments at 9.
    \151\ Potomac Economics Reply Comments at 7.
    \152\ Id. at 11.
    \153\ CAISO DMM Comments at 2, 4.

---------------------------------------------------------------------------

[[Page 2256]]

    69. State government agencies are also mostly supportive of the 
proposed AAR requirements.\154\ New England State Agencies state that 
they strongly support the Commission's proposed AAR requirements.\155\ 
New England State Agencies state that the transmission system was built 
on behalf of and paid for by ratepayers, and argue that the Commission 
should take all reasonable steps to protect those ratepayers from 
excessive costs. New England State Agencies contend that the use of 
AARs can be an important tool in this regard.\156\ New England State 
Agencies state that a transmission system operated using AARs may 
provide benefits by possibly: (1) Obviating the need for new 
transmission lines, thus deferring capital costs; \157\ (2) reducing 
reliance on higher cost local reserves which will reduce costs and 
local reserve requirements resulting from an increased ability to flow 
power into load pockets; \158\ and (3) helping with the integration of 
new clean energy resources.\159\ Finally, New England State Agencies 
argue that, because parts of MISO as well as most of ERCOT are already 
employing AARs, there can be no serious argument that AARs are too 
difficult or costly to implement as was suggested by some transmission 
owners.\160\
---------------------------------------------------------------------------

    \154\ New England State Agencies Comments at 10; OMS Comments at 
2; Ohio FEA Comments at 2.
    \155\ New England State Agencies Comments at 10.
    \156\ Id.
    \157\ Id. at 10-11.
    \158\ Id. at 12.
    \159\ Id.
    \160\ Id.
---------------------------------------------------------------------------

    70. OMS states that it supports the NOPR proposal that AAR 
requirements generally apply to all transmission lines and not just 
those with historical congestion.\161\ OMS notes that the most 
expensive energy prices typically occur after unforeseen outages or 
weather events and are not the result of chronic, well understood 
scenarios. However, OMS also states that it does not support requiring 
AARs on those facilities where it is uneconomical or unreliable to do 
so.\162\ OMS contends that the Commission should require RTOs/ISOs to 
develop a process whereby transmission owners transparently work with 
the RTOs/ISOs and market monitors to demonstrate why any exceptions 
from the requirements are justified.\163\
---------------------------------------------------------------------------

    \161\ OMS Comments at 8-10; see also OMS Reply Comments at 7, 
10.
    \162\ OMS Comments at 9.
    \163\ Id.
---------------------------------------------------------------------------

    71. Ohio FEA also supports the AAR NOPR proposal, stating that AARs 
help ratepayers to realize the full benefits of their transmission 
system investment. Ohio FEA explains that the four Ohio transmission 
owners have already recognized the benefits of AARs, as a way of moving 
away from static ratings.\164\ However, UDPU contends that the AAR NOPR 
proposal should be limited to certain historically congested facilities 
until the Commission has better information to assess the costs and 
benefits of broad AAR implementation.\165\
---------------------------------------------------------------------------

    \164\ Ohio FEA Comments at 2-4.
    \165\ UDPU Comments at 1-3.
---------------------------------------------------------------------------

    72. CEA encourages the Commission to further consider the costs 
associated with the proposed changes, as a broader use of AARs may 
over-estimate the benefit to cost ratio. CEA contends that the use of 
AARs presents a significant cost challenge considering the number of 
upgrades required.\166\
---------------------------------------------------------------------------

    \166\ CEA Comments at 2.
---------------------------------------------------------------------------

    73. Other technical experts are also supportive of more accurate 
transmission line ratings.\167\ R Street Institute states that 
understated transmission line ratings can result in increased 
congestion costs and underutilization of generation in export-
constrained locales, which is disproportionately zero-emission 
generation.\168\ R Street Institute contends that the Commission should 
require DLRs by default and permit exceptions where justified by a 
cost-benefit analysis.\169\
---------------------------------------------------------------------------

    \167\ R Street Institute Comments at 1; WATT Comments at 1-2; 
LineVision Comments at 1-2.
    \168\ R Street Institute Comments at 1.
    \169\ Id. at 3, 5-7.
---------------------------------------------------------------------------

    74. WATT supports the direction the Commission is taking with the 
NOPR's AAR requirements, but explains that additional factors that 
affect transmission line ratings but are not incorporated into AARs are 
very knowable.\170\ WATT contends that the Commission should require 
the use of DLRs when certain criteria are met.\171\ LineVision supports 
WATT's comments and states that DLR implementation will also result in 
additional accuracy and situational awareness.\172\
---------------------------------------------------------------------------

    \170\ WATT Comments at 1-2.
    \171\ Id. at 10-12.
    \172\ LineVision Comments at 1-2.
---------------------------------------------------------------------------

    75. Renewable energy advocates are also generally supportive of the 
AAR NOPR proposal, but urge the Commission to take further measures to 
spur the implementation of DLRs.\173\ For example, ACORE commends the 
Commission for issuing the NOPR, but recommends the Commission take 
further steps to encourage DLR deployment by incenting its deployment 
through transmission incentives and incorporating its assessment into 
transmission planning processes.\174\ Similarly, Clean Energy Parties 
contend that AARs are easy to implement and a modest improvement over 
static line ratings.\175\ However, Clean Energy Parties argue that DLR 
is superior to AAR, though Clean Energy Parties do not contend a 
blanket DLR mandate is appropriate.\176\ ACPA/SEIA support accurate 
transmission line ratings, and contend that the Commission should 
require all transmission owners and transmission providers to study the 
costs and benefits of implementing DLRs on persistently congested 
transmission lines and require implementation where warranted.\177\ 
ACPA/SEIA and Clean Energy Parties both argue that the Commission 
should alter its NOPR proposal to prioritize transmission lines that 
are expected to be congested, persistently congested, or likely to be 
congested in the future.\178\
---------------------------------------------------------------------------

    \173\ ACORE Comments at 1; Clean Energy Parties Comments at 2, 
4-6.
    \174\ ACORE Comments at 1.
    \175\ Clean Energy Parties Comments at 4-5.
    \176\ Id. at 5, 8.
    \177\ ACPA/SEIA Comments at 5-7.
    \178\ Id. at 8-9; Clean Energy Parties Comments at 8, 10.
---------------------------------------------------------------------------

    76. Generator owners and representatives are also generally 
supportive of the proposed AAR requirements.\179\ EDFR argues that 
getting the transmission line rating policy right is important due to 
the urgency of addressing the climate crisis and President Biden's 
carbon emissions reduction goals. EDFR contends that a lack of adequate 
transfer capability can cripple clean energy generation.\180\ EDFR 
further explains that, under many offtake agreements in RTO/ISO 
markets, the developer is paid a fixed price for energy at a market hub 
and if congestion limits the project's ability to deliver power to the 
hub, then the developer bears the risk (known as basis risk). EDFR 
argues that congestion is difficult to hedge in an effective way 
because system topology and conditions change unexpectedly over time, 
but states that more accurate transmission line ratings will decrease 
basis risk and hedging difficulties.\181\ EDFR contends that 
prioritization should not only consider historical congestion, but 
should consider future congestion based on transmission planning, 
interconnection, and transmission service studies for purposes of 
prioritizing implementation.\182\
---------------------------------------------------------------------------

    \179\ ENEL Comments at 1; EDFR Comments at 1-2; Vistra Comments 
at 1-2; EPSA Comments at 2.
    \180\ EDFR Comments at 2.
    \181\ Id.
    \182\ Id. at 4.

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[[Page 2257]]

    77. EPSA contends that the Commission should encourage the use of 
technological advances that improve transmission operators' ability to 
track and optimize transmission line ratings and usage where feasible 
and cost effective. EPSA states that PJM's adoption of AAR requirements 
has shown clear benefits.\183\ Vistra is supportive of the Commission's 
NOPR proposal, stating that it is imperative that the Commission act 
now to make best use of existing infrastructure and that AARs and DLRs 
are the best way to do that.\184\
---------------------------------------------------------------------------

    \183\ EPSA Comments at 2.
    \184\ Vistra Comments at 1-2.
---------------------------------------------------------------------------

    78. Industrial Customer Organizations, TAPS, and Certain TDUs are 
also broadly supportive of the AAR NOPR proposal.\185\ Certain TDUs 
state that they support the proposed rule and encourage the Commission 
to mandate improvements to the accuracy and transparency of 
transmission line ratings because not all transmission owners have 
shown a willingness to make these improvements voluntarily.\186\ 
Certain TDUs state that they support the use of AARs as a way to better 
utilize the existing transmission system, noting that it will become 
imperative that the existing transmission system is utilized to the 
greatest extent possible as additional renewable resources come 
online.\187\
---------------------------------------------------------------------------

    \185\ Industrial Customer Organizations Comments at 1-2; TAPS 
Comments at 1-2; Certain TDU Comments at 1.
    \186\ Certain TDUs Comments at 4.
    \187\ Id. at 4-5.
---------------------------------------------------------------------------

    79. Industrial Customer Organizations state that they generally 
support the proposed rules, but assert that these rules should be 
implemented as soon as practicable.\188\ Industrial Customer 
Organizations argue that, if prioritization is needed, congested 
circuits should be prioritized.\189\ Industrial Customer Organizations 
explain that understated transmission line ratings increase congestion 
and may lead to curtailments. Industrial Customer Organizations contend 
that transmission owners that understate transmission line ratings may 
create an illusory need for transmission upgrades. Further, Industrial 
Customer Organizations contend that some transmission line ratings may 
be deliberately understated because transmission owners may have a 
profit incentive to calculate understated transmission line ratings in 
order to benefit local generation.\190\
---------------------------------------------------------------------------

    \188\ Industrial Customer Organizations Comments at 15-18.
    \189\ Id. at 18-19.
    \190\ Id. at 4.
---------------------------------------------------------------------------

    80. TAPS states that it supports the proposed broad application of 
AARs because it reduces the likelihood that AARs will be implemented in 
a discriminatory manner.\191\ Similarly, Clean Energy Parties cite 
Order No. 888,\192\ in which the Commission stated that ``[d]enials of 
access [to transmission services] (whether they are blatant or subtle), 
and the potential for future denials of access [to transmission 
services], require the Commission to revisit and reform its regulation 
of transmission in interstate commerce.'' \193\ According to Clean 
Energy Parties, Order No. 888 supports the assertion that a lack of 
consistency and transparency in transmission line ratings creates the 
potential for future denials of access to transmission service, as 
inaccurate transmission line ratings are used to provide discriminatory 
transmission service to preferential customers.\194\
---------------------------------------------------------------------------

    \191\ TAPS Comments at 7.
    \192\ Promoting Wholesale Competition Through Open Access Non-
Discriminatory Transmission Services by Public Utilities; Recovery 
of Stranded Costs by Public Utilities and Transmitting Utilities, 
Order No. 888, 61 FR 21540 (May 10, 1996), FERC Stats. & Regs. ] 
31,036 (1996) (cross-referenced at 75 FERC ] 61,080), order on 
reh'g, Order No. 888-A, 62 FR 12274 (Mar. 14, 1997), FERC Stats. & 
Regs. ] 31,048 (cross-referenced at 78 FERC ] 61,220), order on 
reh'g, Order No. 888-B, 81 FERC ] 61,248 (1997), order on reh'g, 
Order No. 888-C, 82 FERC ] 61,046 (1998), aff'd in relevant part sub 
nom. Transmission Access Policy Study Group v. FERC, 225 F.3d 667 
(D.C. Cir. 2000), aff'd sub nom. New York v. FERC, 535 U.S. 1 
(2002).
    \193\ Id. at 31,652.
    \194\ Clean Energy Parties Comments at 2-3.
---------------------------------------------------------------------------

    81. Additionally, TAPS notes that the NOPR proposal would require 
the use of AARs when evaluating requests for near-term point-to-point 
transmission service and contends that the Commission should also apply 
the requirements to requests for near-term secondary service requests 
and near-term network resource designations. TAPS explains that 
secondary service comes ahead of non-firm point-to-point transmission 
service in curtailment priority, and the NOPR proposal flips this 
priority.\195\
---------------------------------------------------------------------------

    \195\ TAPS Comments at 20.
---------------------------------------------------------------------------

    82. Prysmian discourages mandatory AAR implementation without 
consideration of other variables and without a holistic evaluation of 
all transmission line rating inputs to determine whether an overall 
transmission line rating methodology is conservative or not. Prysmian 
states that AARs can also lead to situations in which near-term 
transfer capability is overstated.\196\
---------------------------------------------------------------------------

    \196\ Prysmian Comments at 1.
---------------------------------------------------------------------------

c. Commission Determination
    83. In this final rule, we adopt with certain modifications the 
NOPR proposal to require transmission providers to apply the AAR 
requirements set forth in pro forma OATT Attachment M to all 
transmission lines, subject to the exceptions described below in 
Section IV.D.3.\197\ As discussed above, the AAR requirements will 
ensure that transmission line ratings are more accurate. In turn, more 
accurate transmission line ratings will ensure wholesale rates more 
accurately reflect the cost of the wholesale service being provided 
(i.e., energy, capacity, ancillary services, or transmission service) 
and, thus, that those wholesale rates are just and reasonable. We 
further describe, below, the requirements and the modifications to the 
NOPR proposal adopted herein.
---------------------------------------------------------------------------

    \197\ NOPR, 173 FERC ] 61,165 at PP 92, 102.
---------------------------------------------------------------------------

    84. First, we adopt the proposal to apply the AAR requirements as 
set forth under ``Obligations of Transmission Provider'' in pro forma 
OATT Attachment M to all transmission lines subject to the exceptions 
described below in Section IV.D.3. We find that applying the AAR 
requirements to all transmission lines will both ensure that wholesale 
rates remain just and reasonable and strike an appropriate balance 
between benefits and challenges of AAR implementation. For this reason, 
we do not adopt the phased-in implementation schedule proposed in the 
NOPR in which a transmission provider would initially implement AARs on 
only historically congested lines.
    85. As the Commission preliminarily found in the NOPR \198\ and as 
the record demonstrates, despite differences across transmission 
systems, simply accounting for ambient air temperatures in transmission 
line ratings can reliably increase power transfer capability, resulting 
in significant reliability, operational, and economic benefits. 
Numerous commenters describe these benefits.\199\ For example, Potomac 
Economics estimates that the benefits to AAR implementation in MISO 
alone would have produced approximately $67 million and $49 million in 
reduced congestion costs in 2019 and in 2020,

[[Page 2258]]

respectively.\200\ Exelon describes AARs as a best practice that cost-
effectively enhances transmission utilization, benefiting customers, 
without adverse safety and reliability impacts.\201\ EEI acknowledges 
that experience with AARs shows that their use can provide benefits on 
certain subsets of transmission facilities.\202\ PJM states that, in 
its experience, AARs increase operational flexibility, promote a more 
efficient use of the transmission system, and result in more reliable 
system dispatch and cost-effective market operations.\203\ New England 
State Agencies argue that the Commission should take all reasonable 
steps to protect ratepayers from excessive costs and that the use of 
AARs, by permitting more power to flow than a system operated using 
static or seasonal line ratings, can be an important tool in this 
regard.\204\ Similarly, TAPS explains that reliance on static and 
seasonal line ratings inflicts unnecessary costs on consumers and 
contends that deployment of AARs using commercial temperature forecasts 
can produce significant benefits to consumers at low cost.\205\ While 
several entities note implementation costs as a barrier, these costs 
are mostly initial investment costs in EMS improvements to accommodate 
AARs, implementation of a ratings database, and review (and potentially 
reset) of protective relays settings.\206\ Once these initial 
investments are made, adding AARs to additional transmission lines 
appears to have a minimal incremental cost.\207\
---------------------------------------------------------------------------

    \198\ Id. P 99.
    \199\ MISO Transmission Owners Comments at 8-9; PacifiCorp 
Comments at 2; EEI Comments at 4-5; Entergy Comments at 1-2; BPA 
Comments at 2-4; NYTOs Comments at 2-3, 5; Duke Energy Comments at 
6-7; PG&E Comments at 1; LADWP Comments at 2-3; ITC Comments at 1-3; 
Sunflower Comments at 2; Exelon Comments at 1-2; AEP Comments at 3; 
Indicated PJM Transmission Owner Comments at 2; PJM Comments at 2; 
PJM Comments at 2; New England State Agencies Comments at 7; TAPS 
Comments at 5.
    \200\ Potomac Economics Comments at 7-8.
    \201\ Exelon Comments at 1.
    \202\ EEI Comments at 5.
    \203\ PJM Comments at 2.
    \204\ New England State Agencies Comments at 5-6, 10-11.
    \205\ TAPS Comments at 5.
    \206\ Indicated PJM Transmission Owner Comments at 5-6; Exelon 
Comments at 14; AEP AD19-15 Post Technical Conference Comments at 3.
    \207\ Exelon Comments at 8; Indicated PJM Transmission Owner 
Comments at 5-6; AEP Post-Technical Conference Comments at 2-3; 
September 2019 Technical Conference, Day 1 Tr. at 180-181.
---------------------------------------------------------------------------

    86. Second, in this final rule we adopt a requirement for 
transmission providers to use AARs when evaluating the availability of 
and requests for near-term transmission service (under sections 15, 17, 
18, and 29 of the pro forma OATT).\208\ For purposes of this 
requirement, we define ``requests for near-term transmission service'' 
to include not only requests for near-term point-to-point transmission 
service, but also network resource designations and secondary service 
where the start and end date of the designation/request is within the 
next 10 days. Specifically, we require transmission providers to use 
AARs as the relevant transmission line ratings when: (1) Evaluating 
requests for near-term transmission service, defined as transmission 
service ending within 10 days of the date of the request; (2) 
responding to requests for information on the availability of potential 
near-term transmission service (including requests for ATC or other 
information related to potential service); and (3) posting ATC or other 
information related to near-term transmission service to their OASIS 
site. As discussed further below, in response to comments, we modify 
this requirement from the NOPR proposal to include near-term network 
and near-term secondary service, as well as the near-term point-to-
point transmission service proposed in the NOPR.\209\
---------------------------------------------------------------------------

    \208\ NOPR, 173 FERC ] 61,165 at P 87.
    \209\ Although requests for network transmission service are 
typically long-term requests, meriting their evaluation using 
seasonal line ratings, we note the Commission's finding in Order No. 
890 that the minimum term for network transmission service should be 
the same as the minimum time period used for firm point-to-point 
transmission service (i.e., daily). See Preventing Undue 
Discrimination and Preference in Transmission Service, Order No. 
890, 72 FR 12266 (Mar. 15, 2007), 118 FERC ] 61,119, at P 1505, 
order on reh'g, Order No. 890-A, 73 FR 2984 (Jan. 16, 2008), 121 
FERC ] 61,297 (2007), order on reh'g, Order No. 890-B, 123 FERC ] 
61,299 (2008), order on reh'g, Order No. 890-C, 74 FR 12540 (Mar. 
25, 2009), 126 FERC ] 61,228, order on clarification, Order No. 890-
D, 129 FERC ] 61,126 (2009). As such, any requests for transmission 
service that fall within the near-term threshold defined herein 
would qualify as near-term network transmission service.
---------------------------------------------------------------------------

    87. Third, we adopt the Commission's proposal in the NOPR to 
require that transmission providers use AARs as the relevant 
transmission line rating when determining whether to curtail or 
interrupt near-term point-to-point transmission service (under sections 
13.6 and/or 14.7 of the pro forma OATT) \210\ if such curtailment or 
interruption is both necessary because of issues related to flow limits 
on transmission lines and anticipated to occur (start and end) within 
the next 10 days.\211\
---------------------------------------------------------------------------

    \210\ Additionally, we add references to interruption or 
curtailment of near-term point-to-point transmission service 
occurring pursuant to 13.6 of the pro forma OATT to Attachment M in 
order to ensure consistent treatment of firm and non-firm point-to-
point transmission service.
    \211\ NOPR, 173 FERC ] 61,165 at P 89.
---------------------------------------------------------------------------

    88. Fourth, we adopt the proposal in the NOPR \212\ to require that 
transmission providers use AARs as the relevant transmission line 
ratings when determining whether to curtail network or secondary 
service (under section 33 of the pro forma OATT) or redispatch network 
or secondary service (under sections 30.5 and/or 33 of the pro forma 
OATT), if such curtailment or redispatch is both necessary because of 
issues related to flow limits on transmission lines and anticipated to 
occur (start and end) within 10 days of such determination.
---------------------------------------------------------------------------

    \212\ Id. P 90.
---------------------------------------------------------------------------

    89. Fifth, we adopt and modify the proposal in the NOPR to allow 
RTOs/ISOs to comply with the final rule's AAR requirements by revising 
their OATTs to require implementation of AARs within their security 
constrained economic dispatch (SCED) and security constrained unit 
commitment (SCUC) models (and in any relevant related models) in both 
the day-ahead and real-time markets and reliability unit commitment 
(RUC) processes,\213\ and any other intra-day RUC processes.\214\ As 
the Commission recognized in the NOPR, such entities have Commission-
approved variations from the pro forma OATT to manage congestion and 
initiate curtailments and/or redispatch of transmission service within 
their footprints (although generally not at their borders) through 
mechanisms such as SCED and SCUC. As discussed in Section IV.B.3.b, we 
adopt the Commission's NOPR proposal to require that transmission 
providers--including RTOs/ISOs--update their AARs at least hourly. As 
discussed in Sections IV.B.3.b and IV.B.3.c, for any seams-based 
transmission service offered by RTOs/ISOs, we adopt the Commission's 
NOPR proposal to implement the near-term transmission service 
requirements for inclusion of up-to-date hourly AAR calculations in 
ATC.
---------------------------------------------------------------------------

    \213\ After the day-ahead market process takes place, RTOs/ISOs 
typically perform one or more residual unit commitment processes, or 
what we refer to here as RUC, to address remaining resource gaps and 
reliability issues or to manage uncertainty and the potential for 
real-time operational issues. The exact names, definitions, and 
market processes implementing what we refer here to as RUC processes 
differ across RTOs/ISOs. For example, CAISO refers to its process as 
residual unit commitment, SPP uses reliability unit commitment, and 
MISO uses reliability assessment commitment. For simplicity, 
however, this final rule uses the term RUC to refer to all of these 
relevant processes in all of the RTO/ISO markets interchangeably.
    \214\ NOPR, 173 FERC ] 61,165 at P 91. The statement ``(and in 
any relevant related models)'' was intended to encompass all RUC 
processes within the timeframe. In the interest of clarity, we 
modify the NOPR proposal here to make that more explicit.
---------------------------------------------------------------------------

    90. We do not adopt the NOPR proposal to establish a definition of 
historically congested transmission lines. Accordingly, since we are 
not adopting the NOPR's proposed definition of historically congested 
transmission line, and instead apply the AAR requirements adopted 
herein to all transmission lines, we do not address comments related to 
the NOPR's proposed definition of historically congested transmission 
line. To the

[[Page 2259]]

extent that commenters were arguing for a narrower application than 
what we adopt in this final rule, below we explain the basis for 
application of the AAR requirements to all transmission lines.
    91. Finally, we alter the proposed compliance schedule. 
Specifically, we require each transmission provider to submit a 
compliance filing within 120 days of the effective date of this final 
rule to incorporate into its OATT the changes adopted herein consistent 
with pro forma OATT Attachment M and the changes to the Commission's 
regulations set forth below. Additionally, we further require that all 
requirements adopted herein be fully implemented no later than three 
years from the compliance filing due date established by this final 
rule.
    92. In response to comments received in response to the NOPR, we 
modify the NOPR proposal's defined term ``near-term point-to-point 
transmission service'' to instead be ``near-term transmission 
service.'' As a result, the AAR requirements will apply to requests for 
near-term network transmission service, near-term secondary service, 
and near-term point-to-point transmission service, provided that such 
service meets the 10-day threshold defined in the near-term 
transmission service definition. We agree with TAPS that it would be 
inappropriate to apply the AAR requirements only to requests for near-
term point-to-point transmission service and not to requests for near-
term network and near-term secondary service because secondary service 
comes before non-firm point-to-point transmission service in 
curtailment priority.\215\ More generally, we find that a requirement 
to use AARs on all types of near-term transmission service will better 
ensure that transmission line ratings are accurate and that wholesale 
rates are just and reasonable.
---------------------------------------------------------------------------

    \215\ TAPS Comments at 18-20.
---------------------------------------------------------------------------

    93. Although commenters broadly raise concerns with adopting 
transmission line ratings that may fluctuate widely or contend that 
implementing AARs on certain transmission lines may not yield benefits, 
we do not find that these concerns and arguments overcome the need to 
improve the accuracy of transmission line ratings through applying the 
AAR requirements to all transmission lines. Specifically, we decline to 
accommodate requests for more targeted AAR requirements in which 
transmission providers would either have flexibility to identify 
candidate transmission lines or the Commission would require AAR 
implementation on only priority transmission lines, such as only on 
historically congested lines.
    94. We recognize commenters' concerns, such as those from NRECA/
LPPC, that the promised benefits, costs, and risks of implementing AARs 
may not be evenly distributed nationwide.\216\ Nevertheless, we find 
that with the broad AAR requirements adopted herein, the overall 
benefits via savings to load and lower congestion charges to generators 
will on balance outweigh the costs. Moreover, we acknowledge the 
difficulty of knowing in advance all the locations and situations in 
which the benefits of AAR implementation will outweigh the costs. Given 
the difficulty in predicting unexpected congestion before it happens, 
narrowing the scope of the AAR requirements would limit the ability of 
these reforms to ensure just and reasonable wholesale rates. In 
particular, we find that the AAR requirements adopted in this final 
rule are beneficial in mitigating the impact of transient congestion, 
i.e., temporary or short-term congestion that does not occur on a 
regular basis, such as congestion caused by unexpected equipment 
outages or other unusual conditions. Furthermore, given the increasing 
occurrence of extreme weather events, we expect that assessing the 
benefits of broader AAR implementation based on historical congestion 
likely understates the potential savings associated with implementation 
of the AAR requirements adopted in this final rule. By contrast, the 
record demonstrates that AAR implementation costs are predominantly 
one-time investment costs in EMS improvements to accommodate AARs, 
implementation of a ratings database, and review (and potentially 
reset) of protective relays settings.\217\ Once these costs have been 
incurred, the incremental cost of applying AARs to additional 
transmission facilities is minimal.\218\
---------------------------------------------------------------------------

    \216\ NRECA/LPPC Comments at 15.
    \217\ Exelon Comments at 8-9.
    \218\ Id. at 8; Indicated PJM Transmission Owner Comments at 5-
6; AEP Post-Technical Conference Comments at 2-3; September 2019 
Technical Conference, Day 1 Tr. at 180-181.
---------------------------------------------------------------------------

    95. Attempts to anticipate the situations in which AARs will not be 
cost beneficial (e.g., attempts to forecast locations and situations in 
which there will be future congestion and deploy AARs in only those 
anticipated situations) will necessarily be imperfect and complex, 
especially during infrequent but consequential events. Additionally, 
since many emergencies may come and go before new AARs can be developed 
and implemented for newly congested transmission lines, a more targeted 
AAR requirement advocated by some commenters may not accurately 
represent system transfer capability in such critical situations. As 
the Commission recognized in the NOPR, congestion is difficult to 
predict, particularly during emergency conditions.\219\ The 2019 FERC 
and NERC Staff Report on the January 2018 South Central cold weather 
event illustrates this point.\220\ As shown by that event, during times 
of emergency or system stress, flows may change considerably from 
normal operations and the increased transfer capability provided 
through AARs may prove valuable even on transmission lines that are not 
typically congested.\221\ In addition, in the February 2021 cold 
weather event, MISO experienced unprecedented east-to-west flows 
throughout the footprint and accrued $773 million in congestion charges 
in just a few days.\222\ We note that with broad AAR implementation, 
given Potomac Economics' finding that AAR implementation consistently 
results in savings of approximately 5% to 8% of total congestion,\223\ 
congestion cost savings from this single event might have exceeded the 
total costs of AAR implementation in the region. Moreover, many argue 
that the changing generation mix makes congestion prediction even more 
difficult.\224\ Additionally, AAR implementation itself will have 
secondary consequences for congestion patterns, as changes to 
transmission line ratings may change generation dispatch patterns and, 
by extension, congestion patterns. Such secondary congestion 
consequences may only be able to be promptly addressed by a broad AAR 
requirement that applies to all transmission lines.
---------------------------------------------------------------------------

    \219\ NOPR, 173 FERC ] 61,165 at P 93.
    \220\ 2019 FERC and NERC Staff Report, The South Central United 
States Cold Weather Bulk Electric System Event of January 17, 2018, 
at 96 (July 2019) (FERC and NERC Staff Report), https://www.ferc.gov/sites/default/files/2020-05/07-18-19-ferc-nerc-report_0.pdf.
    \221\ NOPR, 173 FERC ] 61,165 at P 93.
    \222\ OMS Comments at 10; OMS Reply Comments at 7; see FERC, 
NERC and Regional Entity Staff Report, The February 2021 Cold 
Weather Outages in Texas and the South Central United States (Nov. 
16, 2021), https://www.ferc.gov/media/february-2021-cold-weather-outages-texas-and-south-central-united-states-ferc-nerc-and.
    \223\ Potomac Economics Comments at 8; Potomac Economics Post-
Technical Conference Comments at 5-6.
    \224\ ACPA/SEIA Comments at 8, 11; EPSA Comments at 4; New 
England State Agencies Comments at 6.
---------------------------------------------------------------------------

    96. Beyond congestion costs, during times of stressed system 
conditions, operators in RTOs/ISOs might have to

[[Page 2260]]

spend limited time requesting AARs from transmission owners on an ad 
hoc basis.\225\ AAR implementation on all transmission lines will help 
ensure transmission providers have sufficient transfer capability and 
flexibility to manage emergency conditions. Delayed access to AARs 
could force transmission operators to spend precious time reaching out 
to transmission owners for AARs, rather than using such time to manage 
emergency conditions. Instead, AAR implementation on all transmission 
lines will alleviate the need for transmission providers to spend time 
requesting AARs when there may be no time to waste.
---------------------------------------------------------------------------

    \225\ OMS Reply Comments at 7; see also FERC and NERC Staff 
Report at 56-59; ISO-NE, Cold Weather Operations: December 24, 
2017--January 8, 2018, at 41 (Jan. 16, 2019), https://www.iso-ne.com/static-assets/documents/2018/01/20180112_cold_weather_ops_npc.pdf.
---------------------------------------------------------------------------

    97. Further, arguments that the benefits of broad AAR 
implementation will not outweigh the costs are inconsistent with the 
ERCOT and PJM transmission owners' actual AAR implementation 
experience. AEP has been implementing AARs for decades and has realized 
both reliability and financial benefits for its customers.\226\ As 
Indicated PJM Transmission Owners state, transmission owners in PJM 
provide AARs for each of their facility ratings.\227\ PJM further 
states that the use of AARs is commonplace among the overwhelming 
majority of transmission owners in PJM.\228\ As New England State 
Agencies observe, the broad experience implementing AARs does not 
support the argument that AARs are too difficult or costly to 
implement.\229\
---------------------------------------------------------------------------

    \226\ AEP Comments at 3.
    \227\ Indicated PJM Transmission Owners Comments at 6-7.
    \228\ PJM Comments at 2.
    \229\ New England State Agencies Comments at 11-12.
---------------------------------------------------------------------------

    98. In response to MISO Transmission Owners' argument that the 
Commission should not rely on Potomac Economics' estimates of the 
benefits of AARs, our rationale for the AAR requirements adopted in 
this final rule is not solely based on Potomac Economics' analysis. 
Rather, our rationale is based on the finding that AARs on all 
transmission lines will ensure that wholesale rates more accurately 
reflect the cost of the wholesale service being provided, and, thus 
that those wholesale rates are just and reasonable. This finding is 
further informed by the widespread benefits experienced by commenters 
implementing AARs broadly in PJM and ERCOT, the expectation that the 
benefits of AAR implementation will be greatest on transmission lines 
that are frequently congested, along with the understanding of the 
difficulty of predicting congestion and the low incremental cost to 
implement AARs. However, in response to MISO Transmission Owners' 
critique that Potomac Economics' analysis erroneously assumes that all 
transmission lines in MISO are ambient adjustable, we note that, in 
response to MISO Transmission Owners' comments, Potomac Economics 
states that its analysis does not assume that all transmission lines 
are able to be rated using AARs and instead removes from the analysis 
all transmission lines that currently have summer ratings equal to 
winter ratings.\230\ With respect to MISO Transmission Owners' argument 
that Potomac Economics' analysis erroneously assumes that all 
transmission lines in MISO are currently using worst-case ambient air 
temperature assumptions, we note that Potomac Economics does not 
uniformly assume worst-case 104 degrees Fahrenheit as the basis for 
adjusting AARs, but instead infers unique transmission owner base 
assumptions using maximum historical temperatures in each transmission 
owner service territory.\231\ Finally, we disagree with MISO 
Transmission Owners' assertion that the benefits in Potomac Economics' 
analysis are inflated because of certain transmission outages or 
upgrades assumptions. As Potomac Economics explains, there are many 
generalized and localized factors that might increase or decrease 
congestion in an individual year and, given the highly complex nature 
of the electric system, incorporating all of these factors is not 
possible.\232\ Despite certain generalizations, which we believe are 
likely to render Potomac Economics' analysis conservative, Potomac 
Economics has consistently found that AARs and emergency ratings will 
reduce congestion by 10% to 15% annually.\233\
---------------------------------------------------------------------------

    \230\ Potomac Economics Reply Comments at 3-5.
    \231\ Id. at 2-3.
    \232\ Id. at 5-6.
    \233\ Id. at 5.
---------------------------------------------------------------------------

    99. We disagree with arguments from Southern Company, EEI, and 
other commenters that reliability issues may arise because AARs may 
create difficulties in identifying the most limiting element and 
similar difficulties and costs associated with complying with 
Reliability Standard PRC-023-4's transmission relay loadability 
requirements that depend on maximum published ratings. Reliability 
Standard PRC-023-4 requires setting transmission line relays at values 
at or above 115 to 170% of various maximum values for current or power 
carrying capability, e.g., 115% of the highest seasonal 15-minute 
Facility Rating of a circuit or 150% of the highest seasonal four-hour 
Facility Rating of a circuit. We do not agree that this final rule will 
result in PRC-023-4 related relay setting changes to ``thousands'' 
\234\ of relays, since the relay settings are currently calculated 
based on practical limitations which in the majority of cases should 
not exceed AAR values. In addition, PJM has long implemented AARs and, 
rather than describing reliability challenges, contends that AAR 
implementation creates reliability benefits.\235\ For example, PJM 
states that the adoption of AARs increases operational flexibility, 
promotes a more efficient use of the transmission system, and results 
in more reliable system dispatch and cost-effective market 
operations.\236\ Transmission owners in PJM have implemented AARs 
despite the initial cost incurred to update relay settings. Likewise, 
AEP submits that it has implemented AARs for decades and that AAR 
implementation presents reliability benefits.\237\
---------------------------------------------------------------------------

    \234\ EEI Comments at 5-6.
    \235\ PJM Comments at 7.
    \236\ Id. at 2.
    \237\ AEP Comments at 3.
---------------------------------------------------------------------------

    100. In response to concerns about the additional challenges 
associated with incorporating AARs into ATC, as raised by Duke Energy, 
EEI, and several non-RTO/ISO transmission owners with service 
territories in the Western Interconnection, we note that such TTC 
calculation practices, and in turn ATC practices, particularly those 
which only update TTC values annually,\238\ will need to be updated in 
order to comply with this final rule's AAR requirements. In fact, such 
practices may already be out of compliance with the Commission's 
existing ATC calculation rules. For example, while Order No. 890 
provides transmission providers with significant flexibility in what 
approach they take to determine ATC in their transmission paths, it 
also requires that ATC values (regardless of the approach used to 
calculate them) be ``updated and benchmarked to actual events.'' \239\ 
Furthermore, in May 2021, the Commission issued Order No. 676-J,\240\ 
in which the Commission (among other things) codified the 
``fundamentals of Order No. 890 requirements for calculating ATC'' in 
the Commission's regulations.\241\ Specifically, Order No.

[[Page 2261]]

676-J revised section 37.6(b)(2)(i) of the Commission's regulations to 
codify that ATC calculations must be ``conducted in a manner that is . 
. . consistent with anticipated system conditions and outages for the 
relevant timeframe.'' \242\ We find that transmission line ratings 
represent one such ``system condition'' with which ATC calculations 
must be consistent.
---------------------------------------------------------------------------

    \238\ EEI Comments at 11.
    \239\ Order No. 890, 118 FERC ] 61,119 at P 290.
    \240\ Standards for Business Practices and Communication 
Protocols for Public Utilities, Order No. 676-J, 86 FR 29491 (June 
2, 2021), 175 FERC ] 61,139 (2021).
    \241\ Id. P 38.
    \242\ Id.
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    101. In response to specific concerns from PacifiCorp and BPA about 
nomogram constraints, we note that nomogram constraints are typically 
used to represent transfer capability on facilities with stability or 
voltage limitations. The AAR requirements adopted in pro forma OATT 
Attachment M exempt transmission lines whose ratings are not affected 
by ambient air temperature.
    102. In response to comments from NERC requesting further 
consideration of AAR implementation on long transmission lines, and 
from LADWP, and other, primarily western transmission owners, which 
describe AAR implementation challenges due to the diversity in terrain 
and microclimates that western transmission lines traverse, we agree 
that longer transmission lines can and will experience differing 
weather conditions across the length of those transmission lines. To 
maintain reliable system operations, we expect transmission providers 
to implement the transmission line rating calculated based on the most 
limiting element under the prevailing weather conditions (actual or 
anticipated) at the relevant point on the transmission line. In the 
case of transmission conductors, which might be exposed to different 
weather conditions along the length of the transmission line, 
transmission providers must rate such elements using the most limiting 
weather conditions, in accordance with good utility practice. However, 
this requirement does not require the installation of field devices or 
sensors, as some transmission owners suggest.\243\ Rather, as proposed 
in the NOPR, the AAR requirements can be met through the use of a 
weather data service.\244\
---------------------------------------------------------------------------

    \243\ WAPA Comments at 7-9; PG&E Comments at 9-10.
    \244\ NOPR, 173 FERC ] 61,165 at P 95.
---------------------------------------------------------------------------

    103. Similarly, in response to comments from BPA that if BPA uses 
AARs as proposed, it would need to make its current liberal wind 
assumptions (and therefore, the resultant transmission line ratings) 
more conservative to mitigate the risk of operating near the conductor 
limit,\245\ we reiterate that the AAR requirements will ensure more 
accurate transmission line ratings, not necessarily higher transmission 
line ratings. We further clarify that there is no requirement to change 
wind speed assumptions. Utilities have operated reliably for decades 
with AARs.\246\ However, if any transmission owner finds it necessary 
to change its wind speed assumptions consistent with good utility 
practice, we clarify that nothing in this rulemaking prevents it from 
doing so.
---------------------------------------------------------------------------

    \245\ BPA Comments at 4.
    \246\ AEP Comments at 3.
---------------------------------------------------------------------------

2. Specific AAR Implementation Requirements
a. Use of AARs 10-Days Forward in Transmission Service and Operations
i. NOPR Proposal
    104. In the NOPR, within the context of the AAR requirements 
described and adopted above in Section IV.B.1, the Commission proposed 
to apply the AAR requirements to transmission service that starts/ends 
within 10 days, to the curtailment or interruption of point-to-point 
transmission service anticipated to occur (start and end) within the 
next 10 days, and to the curtailment of network transmission service or 
secondary service or redispatch network transmission service or 
secondary transmission service anticipated to occur (start and end) 
within 10 days (hereinafter referred to as the ``10-day threshold'').
    105. The Commission justified the proposed 10-day threshold as a 
reasonable cut-off beyond which forecasts may not be accurate enough 
for AARs to provide significant value, and by stating that the 
Commission believed that such a limit would reasonably accommodate 
requests for weekly point-to-point transmission service. The Commission 
further noted that ambient air temperature forecasts for intervals 
beyond the proposed 10-day threshold tend to converge to the longer-
term ambient air temperature forecasts used in seasonal line 
ratings.\247\ Finally, the Commission noted that its proposal allowed 
transmission providers to determine (consistent with good utility 
practice) the needed degree of certainty when constructing their 
forecasts of ambient air temperature.\248\
---------------------------------------------------------------------------

    \247\ NOPR, 173 FERC ] 61,165 at PP 87-88.
    \248\ Id. P 102.
---------------------------------------------------------------------------

    106. With respect to RTOs/ISOs, the Commission proposed to require 
AARs as the relevant transmission line rating for any point-to-point 
transmission service offered (e.g., at their borders). However, the 
Commission also recognized that RTOs/ISOs have Commission-approved 
variations from the pro forma OATT to manage internal congestion and 
initiate curtailments and/or redispatch of transmission service within 
their footprints through mechanisms such as SCED and SCUC. To 
accommodate these variations, the Commission proposed that RTOs/ISOs 
comply with the proposed requirements by revising their OATTs to 
require implementation of AARs within their SCED and SCUC models (and 
in any relevant related models) in both the day-ahead and real-time 
markets and any intra-day RUC processes. For real-time markets, the 
Commission proposed that RTOs/ISOs update their AARs at least hourly. 
For any point-to-point transmission service offered by RTOs/ISOs (e.g., 
at their borders), the Commission proposed that the AAR requirements 
discussed above for point-to-point transmission service would apply. As 
justification, the Commission explained that day-ahead markets already 
rely upon forecasts of weather to inform next-day load and intermittent 
generation availability. The Commission preliminarily agreed with PJM 
that temperatures can be forecast with a reasonable degree of certainty 
in day-ahead markets.\249\ The Commission further stated that, within 
its NOPR proposal, transmission providers could (consistent with good 
utility practice) determine the needed degree of certainty when 
constructing their forecasts of ambient air temperature, and that, 
because one of the goals of the day-ahead market is to align prices 
with those eventually determined in the real-time market, maintaining 
policy consistency between the day-ahead and real-time markets, where 
practical, is desirable.\250\
---------------------------------------------------------------------------

    \249\ PJM Post-Technical Conference Comments at 3.
    \250\ NOPR, 173 FERC ] 61,165 at P 102.
---------------------------------------------------------------------------

ii. Comments
    107. Many commenters generally support the Commission's proposed 
AAR requirements without specifically discussing the 10-day 
threshold.\251\ Industrial Customer Organizations specifically agree 
with the Commission that implementing AARs in near-term transmission 
service will more accurately reflect the cost of delivering

[[Page 2262]]

energy to load.\252\ CEA states that using AARs to calculate 
transmission line ratings for service requests up to 10 days has proven 
to be reliable and to provide benefits to effective and reliable 
transmission operations.\253\ EDFR contends that the distinction 
between AARs and seasonal line ratings depending on the applicable time 
frame appears sensible.\254\ ACPA/SEIA state that they support the 
Commission's proposed requirements for near-term point-to-point 
transmission service and curtailments expected to occur within the next 
10 days.\255\ The Ohio FEA does not take a firm position, but states 
that implementing AARs for the next 10 days is reasonable.\256\ OMS 
states that the weather data required to implement AARs is already 
widely available through public sources and used for load and resource 
forecasting.\257\
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    \251\ EPSA Comments at 2; Clean Energy Parties Comments at 2-3; 
R Street Institute Comments at 2-3; TAPS Comments at 1-3; ACORE 
Comments at 3; OMS Comments at 2; New England State Agencies 
Comments at 10; Vistra Comments at 2-3.
    \252\ Industrial Customer Organizations Comments at 4-6.
    \253\ CEA Comments at 2.
    \254\ EDFR Comments at 7.
    \255\ ACPA/SEIA Comments at 16-17.
    \256\ Ohio FEA Comments at 5.
    \257\ OMS Comments at 11.
---------------------------------------------------------------------------

    108. While not supporting or opposing the proposed 10-day 
threshold, EPRI recommends an independent assessment that documents the 
accuracy and risk associated with weather forecast data, explaining 
that not all weather forecast data will be appropriate for transmission 
line ratings and that some limiting spans run through microclimates. 
EPRI further explains that inaccurate forecast risks can be mitigated 
by identifying and implementing corrective factors to allow forecasts 
to be used consistent with good utility practice. EPRI suggests 
utility-specific rating studies would be required to assess and 
mitigate forecast risk,\258\ to update and revise weather condition 
assumptions, and possibly to adjust transmission reliability 
margins.\259\ EPRI contends that further studies are needed to 
determine a technical basis for updated wind speed assumptions and that 
such studies may take between one and two years.\260\ Similarly, NERC 
asserts that the Commission should consider how variations in the 
temperature and load forecast should be addressed, what temperature 
sets should be used when considering requests to grant firm 
transmission service, and whether additional AAR calculation 
information should be incorporated into transmission line rating 
methodologies.\261\
---------------------------------------------------------------------------

    \258\ EPRI Comments at 10-11.
    \259\ Id. at 12. Transmission reliability margin, or TRM, means 
the amount of TTC necessary to provide reasonable assurance that the 
interconnected transmission network will be secure, or such 
definition as contained in Commission-approved Reliability 
Standards. 18 CFR 37.6(b)(1)(viii) (2021)..
    \260\ EPRI Comments at 12.
    \261\ NERC Comments at 7.
---------------------------------------------------------------------------

    109. Other commenters also discuss risk management for forecasted 
ambient air temperatures. For example, Entergy states that forecasted 
ambient air temperatures should include appropriate safety margins to 
account for historical forecast uncertainty.\262\ Similarly, the SPP 
MMU states that, ideally, congestion costs should, to some extent, 
represent the risk assumed to serve the load.\263\ Finally, the CAISO 
DMM argues that AAR requirements should allow leeway for RTOs/ISOs to 
adjust modeled transmission limits for reliability reasons, as CAISO 
does in the case of flowgates and nomograms whose modeled flows 
frequently differ from actual flows.\264\ The CAISO DMM asserts that 
lower or more conservative transmission limits might be needed for 
temporally distant intervals to ensure commitments made in an advisory 
interval horizon are feasible in the binding market interval and at the 
time of power flow. The CAISO DMM further asserts that lower day-ahead 
transmission limits could promote the feasibility of day-ahead 
commitments in real time.\265\
---------------------------------------------------------------------------

    \262\ Entergy Comments at 11.
    \263\ SPP MMU Comments at 1.
    \264\ CAISO DMM Comments at 3, 4-5, 7.
    \265\ Id. at 3.
---------------------------------------------------------------------------

    110. Many RTOs/ISOs, however, oppose or urge caution on the 
proposed 10-day threshold, with many advocating instead for a 48-hour 
threshold.\266\ PJM does not support use of AARs in ATC calculations 
beyond 48 hours, arguing that it would require significant system 
changes and increase the compliance burden.\267\ PJM proposes AARs for 
48 hours, and a more conservative approach for hours 48-240 to avoid 
potential volatility and over-selling.\268\ Both NYISO and ISO-NE argue 
that the transmission service offered in their respective regions 
differs from that contemplated by the pro forma OATT, and request 
flexibility in implementing any transmission line rating 
requirements.\269\
---------------------------------------------------------------------------

    \266\ PJM Comments at 7-8; ISO-NE Comments at 10; MISO Comments 
at 10, 16-17; NYISO Comments at 13-14.
    \267\ PJM Comments at 7-8.
    \268\ Id.
    \269\ ISO-NE Comments at 10; NYISO Comments at 9.
---------------------------------------------------------------------------

    111. NYISO does not support extending the AAR requirements or DLRs 
into the day-ahead market, or for use up to 10 days into the future, 
contending that such a requirement could result in costly and 
unnecessary uplift payments, which could lead to significant cost 
increases to customers, and could present reliability concerns if 
transmission line ratings decline in real time from the day-ahead 
schedule, forcing NYISO to rapidly reduce the schedules of certain 
generators while quickly ramping up other generators.\270\ NYISO also 
states that it would consider designating a portion of transfer 
capability to be able to respond to the operational and cost volatility 
that would come with DLR use, although such a process would limit 
overall efficiency and increase production costs.\271\
---------------------------------------------------------------------------

    \270\ NYISO Comments at 13-14.
    \271\ Id.
---------------------------------------------------------------------------

    112. Without taking a position on the proposed 10-day threshold, 
CAISO explains that the NOPR proposal would significantly increase the 
complexity of its day-ahead market and introduce possible variances 
between real-time and day-ahead schedules.\272\ Also without taking a 
position on the proposed 10-day threshold, SPP states that, to use AARs 
to evaluate transmission service requests that end within 10 days or as 
the basis for curtailment, SPP would have to make several technical and 
process upgrades and align its operating horizon and planning 
horizon.\273\
---------------------------------------------------------------------------

    \272\ CAISO Comments at 9-11.
    \273\ SPP Comments at 5-7, 9.
---------------------------------------------------------------------------

    113. MISO argues that the vast majority of the benefit from AARs is 
in addressing real-time congestion, and that implementing AARs in 
MISO's day-ahead market would be difficult to do in less than three 
years, while offering comparatively little benefit. MISO further claims 
that requiring hourly AARs 10 days in advance will provide little to no 
benefit because the accuracy of temperature forecasts diminishes 
considerably beyond 48 hours, and precipitously by the five to seven 
day mark.\274\ MISO urges the Commission to limit AAR implementation to 
48 hours from the start of the operating day.\275\ Similarly, Potomac 
Economics recommends that the Commission require that AARs be used in 
the day-ahead and real-time markets, stating that this will allow the 
RTOs/ISOs to focus their resources on improving the transmission line 
ratings that will generate almost all of the savings.
---------------------------------------------------------------------------

    \274\ MISO Comments at 18.
    \275\ Id. at 19.
---------------------------------------------------------------------------

    114. Similar to RTOs/ISOs, transmission owners also urge caution 
on, or oppose, the proposed 10-day threshold.\276\ Those transmission

[[Page 2263]]

owners generally argue that there is too much risk forecasting 10 days 
forward and generally support more limited forecasting of either 24 
\277\ or 48 hours.\278\ For example, Indicated PJM Transmission Owners 
contend that forecasting AARs beyond two or three days in advance 
provides little benefit because weather conditions beyond that are too 
difficult to predict.\279\ Dominion similarly argues there is no 
benefit to extending the AAR requirements beyond three to five days 
because forecasts beyond five days tend to reflect seasonal 
averages.\280\ Entergy contends that forecasts should be limited to 
three days and include appropriate safety margins for historical 
forecast uncertainty and geographic variability.\281\
---------------------------------------------------------------------------

    \276\ BPA Comments at 7; Indicated PJM Transmission Owners 
Comments at 2; Dominion Comments at 8-9; Duke Energy Comments at 8-
9; SDG&E Comments at 2-3; Southern Company Comments at 5-6; MISO 
Transmission Owners Comments at 15-16; EEI Comments at 10-11; APS 
Comments at 8; NYTOs Comments at 5-6; AEP Comments at 6-7; NRECA/
LPPC Comments at 19-20; SDG&E Comments at 2-3; LADWP Comments at 7; 
ITC Comments at 7-9.
    \277\ BPA Comments at 7; Duke Energy Comments at 8-9; Southern 
Company Comments at 5-6; MISO Transmission Owners Comments at 15-16; 
EEI Comments at 10-11; APS Comments at 8; NYTOs Comments at 5-6.
    \278\ AEP Comments at 6-7; NRECA/LPPC Comments at 19-20; SDG&E 
Comments at 2-3; LADWP Comments at 7.
    \279\ Indicated PJM Transmission Owners Comments at 2.
    \280\ Dominion Comments at 9.
    \281\ Entergy Comments at 11.
---------------------------------------------------------------------------

    115. Several commenters argue that requiring AARs 10 days in 
advance presents the potential problem of selling transmission service 
based on a given ambient air temperature forecast only for the 
temperature to be higher in real time, causing curtailments or safety 
and reliability risks.\282\ BPA argues that it could result in an 
inefficient use of the transmission system because transmission could 
be sold, curtailed, and then available again, all prior to the 
transmission service window.\283\ NYTOs note that, because there is 
generally less flexibility in real time, if operators do not have 
sufficient resources to restore flow to a lower limit within the 
required time, they may need to shed load or damage equipment.\284\
---------------------------------------------------------------------------

    \282\ MISO Transmission Owners Comments at 15-16; Duke Energy 
Comments at 8-9; Southern Company Comments at 5-6; NYTOs Comments at 
5.
    \283\ BPA Comments at 7.
    \284\ NYTOs Comments at 5-6.
---------------------------------------------------------------------------

    116. Arguing that the Commission should not extend the AAR 
requirements beyond the operating day, MISO Transmission Owners state 
that using AARs any further forward than in real time introduces 
uncertainty and error. MISO Transmission Owners acknowledge that these 
risks exist today, but argue that AARs introduce further complexity and 
explain that lowering transmission line ratings in real time would 
compound the problems.\285\ Similarly, Duke Energy presents an example 
of transmission sold based on a 60 degree Fahrenheit temperature 
forecast four days forward and, on the operating day having the 
transmission system oversubscribed, with greater pressure on operators 
to curtail transmission schedules to avoid safety and reliability 
risks, because the actual temperature was 75 degrees Fahrenheit.\286\ 
Southern Company states that AARs have the potential to create 
reliability concerns if transmission service is oversold due to 
inaccurate weather forecasts, especially for transmission service that 
is scheduled 10 days ahead.\287\ Southern Company also states that 
reliability issues may arise because AARs may create difficulties in 
identifying the most limiting element, which may change as the 
temperature changes, for the purpose of complying with Reliability 
Standard FAC-008-5, and similar difficulties in complying with 
Reliability Standard PRC-023 relay loadability requirements that depend 
on maximum published ratings.\288\
---------------------------------------------------------------------------

    \285\ MISO Transmission Owners Comments at 15-16.
    \286\ Duke Energy Comments at 8-9.
    \287\ Southern Company Comments at 5-6.
    \288\ Id. at 6.
---------------------------------------------------------------------------

    117. NRECA/LPPC contend that such a requirement is unduly 
burdensome because most of the benefits of using AARs are for real-time 
and day-ahead transactions. NRECA/LPPC add that hourly weather 
forecasts and the resulting hourly transmission line ratings are 
unlikely to be accurate for more than a very few days.\289\ IID 
explains that the Commission should provide flexibility in the forward 
AAR application period, noting that weather patterns may not be stable 
everywhere. IID contends that the Commission should consider 
implementation challenges associated with looking 10 days ahead, 
calculating what could be several hundred transmission line ratings per 
year.\290\
---------------------------------------------------------------------------

    \289\ NRECA/LPPC Comments at 19-20.
    \290\ IID Comments at 4-6.
---------------------------------------------------------------------------

    118. EEI and APS contend that AARs should only be implemented in 
real-time operations.\291\ EEI contends that such AAR values should not 
extend to the day-ahead or intra-day unit commitment values and that 
hourly ATC for up to 10 days would introduce uncertainty and ATC 
fluctuations that result in curtailment of sold service and resale of 
previously curtailed service. EEI further explains that the Commission 
has previously recognized the reliability harm associated with 
overestimated ATC and explains that the harm may result from using 
hourly AARs for transmission service available for up to 10 days. EEI 
also states that the NOPR proposal for hourly ATC for every hour in the 
next 10 days is complex, with a burden that may outweigh the benefits 
since the NOPR proposal fundamentally requires a TTC determination. 
However, EEI states that TTC is path dependent and is based on many 
transmission line ratings, contingencies, and power flow assumptions. 
Because of this complexity, some transmission owners only determine TTC 
annually or less frequently and, for these transmission owners, the 
NOPR proposal for transmission providers to recalculate TTC every hour, 
and perform 240 calculations every hour, is infeasible.\292\ NERC 
contends that the Commission should consider how entities should 
reconcile AARs used for planning and operations functions. NERC also 
argues that there is potential confusion regarding transmission line 
ratings used in transmission operator operations and planning system 
operating limits and interconnection reliability operating limits, but 
believes the confusion can be avoided through the timing of Commission 
action to retire the NERC Modeling, Data, and Analysis (MOD) A 
Reliability Standards.\293\
---------------------------------------------------------------------------

    \291\ APS Comments at 8; EEI Comments at 10-12.
    \292\ EEI Comments at 10-12.
    \293\ NERC Comments at 7-8.
---------------------------------------------------------------------------

    119. NYTOs explain that requiring AARs for up to 10 days forward, 
even for a subset of the transmission system, would be a significant 
change requiring major software buildout and corresponding market 
design changes, which would create a significant burden on NYISO and 
its associated utilities. NYTOs assert that this burden would be 
further complicated by the fact that vendor availability for such a 
buildout is unknown.\294\ NYTOs also explain that implementing AARs 10 
days forward has the potential to create reliability concerns through 
disconnects between forecasted and real-time conditions \295\ and that 
extending the AAR requirements to the day-ahead market would make 
security analysis more difficult.\296\ LADWP contends that the 
Commission should align any final rule requirements with NERC 
Reliability Standards and asserts that the proposed 10-day threshold 
would conflict with

[[Page 2264]]

the requirements specified in Reliability Standard MOD-001-1a that ATC 
be calculated hourly for the next 48 hours.\297\ Moreover, recognizing 
the variability in weather, LADWP asks that system operators be 
afforded the flexibility to recall transfer capability awarded during 
moderate conditions at least 24 hours in advance.\298\
---------------------------------------------------------------------------

    \294\ NYTOs Comments at 5-6.
    \295\ Id.
    \296\ Id. at 7.
    \297\ LADWP Comments at 7.
    \298\ Id. at 6.
---------------------------------------------------------------------------

iii. Commission Determination
    120. We adopt the NOPR proposal to require transmission providers 
to use AARs when evaluating the availability of and requests for near-
term transmission service (under sections 15, 17, 18, and 29 of the pro 
forma OATT) \299\ as set forth under ``Obligations of Transmission 
Provider'' in the pro forma OATT Attachment M adopted in this final 
rule. We further adopt the Commission's proposal in the NOPR to require 
transmission providers to use AARs as the relevant transmission line 
rating when determining whether to curtail or interrupt point-to-point 
transmission service (under sections 13.6 and/or 14.7 of the pro forma 
OATT) if such curtailment or interruption is both necessary because of 
issues related to flow limits on transmission lines and anticipated to 
occur (start and end) within the next 10 days. Additionally, we adopt 
the Commission's proposal in the NOPR to require transmission providers 
to use AARs as the relevant transmission line rating when determining 
whether to curtail network or secondary service (under section 33 of 
the pro forma OATT) or redispatch network or secondary service (under 
sections 30.5 and/or 33 of the pro forma OATT), if such curtailment or 
redispatch is both necessary because of issues related to flow limits 
on transmission lines and anticipated to occur (start and end) within 
10 days of such determination (i.e., the 10-day threshold). Finally, 
consistent with the NOPR, we clarify that AARs must be calculated using 
the temperature at which there is sufficient confidence that the actual 
temperature will not be greater than that temperature (i.e., expected 
temperature plus an appropriate forecast margin).\300\
---------------------------------------------------------------------------

    \299\ See supra P 85.
    \300\ See NOPR, 173 FERC ] 61,165 at PP 97, 102.
---------------------------------------------------------------------------

    121. We believe that the 10-day threshold is justified by: (1) The 
additional benefits gained by adopting a threshold that permits weekly 
point-to-point transmission service requests to be evaluated using 
AARs; (2) the additional benefits gained by the use of daytime/
nighttime ratings (discussed below in Section IV.B.2.c) within the 10-
day threshold; (3) the adequate accuracy of ambient air temperature 
forecasts combined with the ability to implement appropriate forecast 
margins to alleviate operational concerns associated with persistently 
decreasing real-time transmission line ratings; and (4) the low 
relative cost difference between a shorter forward threshold and the 
proposed 10-day threshold. As the Commission stated in the NOPR, AAR 
requirements up to 10 days forward will permit weekly point-to-point 
transmission service to be evaluated using AARs. Because weekly point-
to-point transmission service is one of several types of transmission 
products provided under the Commission's pro forma OATT, by adopting 
the 10-day threshold for AAR implementation rather than a shorter 
forward duration, weekly point-to-point transmission customers will 
receive the benefits of AAR implementation rather than only 
transmission customers taking shorter duration transmission service, 
thereby not just increasing the expected benefits from the 
implementation of AARs by improving the accuracy of transmission line 
ratings for a wider range of transmission services but also for a 
potentially wider range of transmission customers.
    122. We also require AARs to include separate daytime and nighttime 
ratings. This daytime/nighttime ratings requirement, combined with the 
addition of weekly point-to-point transmission service, will produce 
further benefits in forward nighttime hours that would not see such 
benefits if the AAR requirements were imposed over a timeframe shorter 
than 10 days forward. These benefits of increased accuracy that result 
from applying daytime/nighttime ratings to weekly point-to-point 
transmission service and to shorter duration transmission service up to 
10 days forward are significant on their own, even in the unlikely 
event that the use of ambient air temperature forecasts 10 days forward 
results in no hours where daytime AARs are greater than seasonal line 
ratings. In other words, if we were to adopt a shorter threshold for 
the AAR requirements than 10 days forward, the significant benefits 
derived from the more accurate transmission line ratings during the 
additional nighttime hours included in the 10-day threshold would be 
lost. We further note that weather forecast quality is not static, but 
rather is steadily improving such that the benefits of the 10-day 
threshold requirement are likely to increase over time.\301\
---------------------------------------------------------------------------

    \301\ See, e.g., NOAA, Annual WPC Mean Absolute Errors, https://www.wpc.ncep.noaa.gov/images/hpcvrf/maemaxyr.gif (last visited Oct. 
28, 2021) (showing NOAA data on the evolving accuracy of their 
Weather Prediction Center forecasts of daily high temperature).
---------------------------------------------------------------------------

    123. Although we acknowledge that the accuracy of forecasts 
decreases the further in advance the forecast is made, we disagree that 
ambient air temperature forecasts made 10 days in advance are so 
inaccurate that they cannot provide any benefits when used as part of 
AARs, even when adjusted with appropriate forecast margins, as 
discussed herein. Neither commenters supporting nor opposing the 10-day 
threshold provide quantitative evidence related to the accuracy of 10-
day forecasts; however, a published analysis of the NOAA National Blend 
of Models (NBM) forecast--one of the publicly available NOAA forecasts 
that looks out at least 10 days--indicates that the mean absolute error 
for 240 hour (10 day) forward continental United States surface 
temperature forecasts was approximately four to six degrees Fahrenheit 
in July to November 2016.\302\ We find that such levels of error would 
likely allow for a meaningful number of hours in any season where a 10-
day forward AAR would provide benefits relative to the seasonal line 
rating. We also note that this finding is consistent with the support 
for the 10-day threshold by various commenters.\303\
---------------------------------------------------------------------------

    \302\ Tabitha Huntemann, Daniel Plumb, and David Ruth, 
Verification of the National Blend of Models (2017), https://www.weather.gov/media/mdl/AMS2017-NBMVerification.pdf. We note that 
this analysis was applicable to the 2016 National Blend of Models 
(NBM) Version 2.0 forecast, and that several improved versions of 
the NBM forecast have been implemented since that time. The current 
NBM Version 4.0 was implemented in September 2020. See NBM: National 
Blend of Models, https://vlab.noaa.gov/web/mdl/nbm. While we take 
notice of this NBM forecast accuracy data as a point of reference, 
we emphasize that the NBM forecasts are just one example of the 
types of forecasts that transmission providers might rely on in 
complying with this final rule.
    \303\ CEA Comments at 2; EDFR Comments at 7; Ohio FEA Comments 
at 5; New England State Agencies Comments at 9-10; ACPA/SEIA 
Comments at 13.
---------------------------------------------------------------------------

    124. We do not find persuasive arguments that the AAR requirements 
adopted in this final rule will be unduly burdensome. Contrary to such 
assertions, because we expect the increased costs of implementing AARs 
under a 10-day threshold (as opposed to a shorter threshold) to be 
primarily related to increased forecasting and data storage/hardware 
needs, we do not expect such costs to be excessive. Moreover, in 
certain situations, especially outside the RTO/ISO context, adopting 
the 10-day threshold will

[[Page 2265]]

allow more transfer capability to be made available to customers than 
simply adopting seasonal worst-case assumptions. In addition, as CEA 
states, using AARs to calculate transmission line ratings for service 
requests up to 10 days has proven to be reliable and to provide 
benefits to effective and reliable transmission operations.\304\ In 
that context, commenters have not provided evidence that the cost to 
procure or develop 10-day forward forecasts is materially different 
from the cost to procure or develop two- or three-day forward forecasts 
and, in any case, that such cost outweighs the added benefits of 
extending the forward period from two or three days to 10 days. For 
these reasons, we expect the material benefits resulting from adopting 
the 10-day threshold to, on balance, outweigh the costs.
---------------------------------------------------------------------------

    \304\ CEA Comments at 2.
---------------------------------------------------------------------------

    125. We emphasize that any benefit from the AAR requirements, and 
the 10-day threshold in particular, should be compared to the relative 
costs of alternatives. And we find that the cost associated with 
requiring AARs for additional days forward is essentially the cost of 
accessing, storing, and processing the additional forecast data, and 
the cost of calculating, storing, and incorporating into transmission 
service the additional hours of AARs. As we expect this process will be 
largely automated, we do not anticipate that the cost of the 10-day 
threshold, as opposed to a shorter threshold, will be significantly 
higher. Although the question of where to draw the line in terms of the 
time threshold for AAR implementation is not clear cut, we find that 10 
days strikes an appropriate balance between the benefits of more 
accurate transmission line ratings that result from the AAR 
requirements adopted in this final rule, and the likely costs of 
implementing those requirements.
    126. We note that some commenters may have misunderstood the 
Commission's proposal in the NOPR as requiring the use of expected 
ambient air temperatures in forecasts of AARs for future periods. That 
is, they may have read the Commission's NOPR proposal as requiring that 
if the forecasted ambient air temperature at a given transmission line 
10 days in advance (without any forecast margin applied, i.e., the 
expected temperature) was X degrees, that the transmission provider was 
required to use an AAR for that hour 10 days forward that assumed an 
air temperature of X degrees. This is not the case. Rather, AARs must 
be calculated using the temperature at which there is sufficient 
confidence that the actual temperature will not be greater than that 
temperature (i.e., expected temperature plus an appropriate forecast 
margin).\305\ This approach to calculations is consistent with EPRI's 
recommendation and also comments from Entergy and the CAISO DMM, which 
suggest margins to account for forecast error.\306\
---------------------------------------------------------------------------

    \305\ See NOPR, 173 FERC ] 61,165 at PP 97, 102.
    \306\ EPRI Comments at 10-12; Entergy Comments at 11; CAISO DMM 
Comments at 3.
---------------------------------------------------------------------------

    127. In response to requests for clarification from BPA, LADWP, and 
EEI that transmission providers can curtail transmission sold at least 
24 hours in advance, consistent with existing curtailment 
prioritization, should temperature forecasts dictate such curtailment, 
we confirm that we are not changing the existing curtailment 
prioritization. In implementing the 10-day threshold, it may be 
necessary in some instances for transmission providers to curtail 
transmission sold based on ambient air temperature forecasts (including 
forecast margins) that end up being lower than real-time temperatures. 
Although transmission providers will continue to curtail transmission 
at times due to unrealized ambient air temperature assumptions, the 
need for such curtailments should be decreased as a result of the AAR 
requirements adopted herein.\307\ We reiterate that under the AAR 
requirements that we adopt in this final rule, transmission providers 
have the latitude (and obligation) to develop accurate, safe, and 
reliable transmission line ratings,\308\ and we do not expect that such 
transmission line ratings will necessitate an increase in the need for 
curtailments due to inaccurate AARs. If a transmission provider 
determines (whether during pre-testing of its AAR methodologies or 
during actual operations) that a given level of forecast margins yields 
an unreasonable frequency of such curtailment, it should re-evaluate 
and adjust its forecast margins.
---------------------------------------------------------------------------

    \307\ We note, for example, that a typical winter seasonal line 
rating temperature assumption today is 32 degrees Fahrenheit--a 
temperature assumption which in many parts of the United States is 
violated frequently over the current typical six-month ``winter 
season'' used in seasonal line ratings. Commission Staff Paper at 7; 
see also Midwest Reliability Organization Standards Committee, 
Standard Application Guide: FAC-008, Version 1.1, p. 14 (March 21, 
2017), https://www.nerc.com/pa/comp/guidance/EROEndorsedImplementationGuidance/FAC-008-3%20Standard%20Application%20Guide.pdf. We expect such assumption 
violations to be less frequent under our required approach, where 
transmission providers will apply reasonable forecast margins when 
developing their AARs
    \308\ NOPR, 173 FERC ] 61,165 at P 97.
---------------------------------------------------------------------------

    128. We further acknowledge that, in addition to the concerns of 
some commenters related to forecast margins being too low, certain 
forecast margins could also prove to be too high. In those instances, 
as with the implementation of static transmission line ratings, 
transmission line ratings using unreasonably high forecast margins 
would also yield inaccurate transmission line ratings and, in turn, 
would result in an underutilization of existing transmission 
facilities, price signals based on less transfer capability than is 
truly available, and wholesale rates that are unjust and unreasonable. 
Similar to unreasonably low forecast margins, if a transmission 
provider determines (whether during pre-testing of its AAR 
methodologies or during actual operations) that a given forecast margin 
is unreasonably high, it should re-evaluate and adjust its forecast 
margins.
    129. Similarly, contrary to comments from CAISO, NYISO, NYTOs, and 
EEI that describe the operational risks associated with overestimating 
ATC,\309\ we do not expect that the AAR requirements adopted herein 
will result in a frequent number of instances when transmission line 
ratings used in the real-time market are lower than transmission line 
ratings used in the day-ahead market. Some such instances will occur, 
but we believe that there is sufficient latitude within our 
requirements, as discussed above, for day-ahead transmission line 
ratings to be determined with sufficient forecast margins to avoid this 
concern. Furthermore, as the Commission stated in the NOPR, day-ahead 
markets already rely heavily upon weather forecasts to inform next-day 
load and intermittent generation availability. This final rule does not 
change reliance upon weather forecasting; instead, the AAR requirements 
we adopt herein will improve the accuracy of transmission line ratings 
and, if anything, lead to cost savings to consumers and reliability 
benefits. Additionally, as PJM's AAR implementation experience 
demonstrates, temperatures can be forecast day ahead with a reasonable 
degree of certainty.\310\ We also find that operational risks that 
might result from the use of transmission line ratings in the real-time 
market that are lower than the transmission line ratings used in the 
day-ahead market can further be

[[Page 2266]]

managed and mitigated through the use of AARs in the RUC processes, 
which will have the benefit of updated temperature forecasts. Finally, 
we reiterate that PJM and AEP report reliability benefits from AAR 
implementation.
---------------------------------------------------------------------------

    \309\ NYTOs Comments at 5-6; EEI Comments at 10-12; NYISO 
Comments at 13-14; CAISO Comments at 9-11.
    \310\ PJM Comments at 3.
---------------------------------------------------------------------------

    130. In response to comments from EEI and other transmission owners 
about the complexities of calculating AARs up to the 10-day threshold, 
we find that such complexities are predominately reflected in the 
upfront set-up and investment costs \311\ and that these costs will be 
primarily related to increased forecasting and data storage/hardware 
needs.
---------------------------------------------------------------------------

    \311\ Exelon Comments at 8; AEP Post-Technical Conference 
Comments at 2-3; see also supra Section IV.B.1.c.
---------------------------------------------------------------------------

    131. In response to NERC's request that the Commission consider how 
entities should reconcile AARs used for planning and operations 
functions,\312\ we find that AARs used in near-term operations will 
deviate from those transmission line ratings used in various planning 
functions. As transmission providers progress closer in time to a given 
interval, near-term ambient air temperature forecasts will necessarily 
be updated. These updates will impact TTC, and, as a result, ATC and 
system operating limits. In addition, regarding implementation of this 
final rule and currently effective MOD A Reliability Standards,\313\ 
this final rule does not advocate for operating the transmission system 
beyond the system operating limits and established facility ratings.
---------------------------------------------------------------------------

    \312\ NERC Comments at 6-7.
    \313\ Id. at 7.
---------------------------------------------------------------------------

    132. In response to requests for clarification of the NOPR proposal 
from NERC and BPA with respect to temperature variations,\314\ 
transmission providers must consider the relevant ambient air 
temperature forecasts along the transmission line, and determine the 
transmission line rating based on the most limiting combination of 
equipment limitations and forecasted local ambient air temperature 
along the transmission line. We note that NERC additionally requested 
that the Commission consider how variations in load forecasts would be 
addressed when using values for each of the 240 hours in the next 10 
days for each transmission line in granting firm point-to-point 
transmission service.\315\ In response, we reiterate that the 
requirements adopted herein are designed to ensure accurate 
transmission line ratings. We also reiterate that AARs must be 
calculated using the temperature at which there is sufficient 
confidence that the actual temperature will not be greater than that 
temperature (i.e., expected temperature plus an appropriate forecast 
margin). We further clarify, in response to NERC, that transmission 
line rating methodologies must be updated. In particular, pro forma 
OATT Attachment M, as adopted by this final rule, requires transmission 
line ratings to be computed in accordance with a written transmission 
line rating methodology and consistent with good utility practice. 
Moreover, we note that Reliability Standard FAC-008-5 Requirement 3.2 
requires transmission line rating methodologies to identify how ambient 
conditions are considered.\316\ Thus, transmission line rating 
methodologies need to document methods used to calculate AARs.
---------------------------------------------------------------------------

    \314\ NERC Comments at 6-7; BPA Comments at 2-4.
    \315\ NERC Comments at 6-7.
    \316\ Reliability Standard FAC-008-5, Requirement R3.2, p.4, 
http://www.nerc.com/pa/Stand/Project%20201803%20Standards%20Efficiency%20Review%20Require/2018-03_FAC-008-5_clean_01192021.pdf.
---------------------------------------------------------------------------

    133. In response to LADWP's argument that the Commission should 
align AAR requirements with the NERC Reliability Standards--and that 
the proposed 10-day threshold would conflict with the requirement 
specified in Reliability Standard MOD-001-1a that ATC be calculated 
hourly for the next 48 hours--we note that Reliability Standard MOD-
001-1a requires that ATC be calculated for at least the next 48 hours, 
not for only the next 48 hours. Furthermore, the Commission's 
regulations require ATC to be calculated and/or posted for periods more 
than 48 hours in the future (e.g., when transmission service is 
requested or inquired about).
    134. Finally, in response to RTO/ISO requests for flexibility, we 
clarify the applicability of the 10-day threshold to RTOs/ISOs. The 
vast majority of energy transactions in RTOs/ISOs are executed and 
financially settled in the day-ahead and real-time energy markets; 
thus, we find that requiring AARs for the real-time and day-ahead 
energy markets in RTOs/ISOs is necessary to ensure the accuracy of 
transmission line ratings and just and reasonable wholesale rates. 
Because these transactions take place within a one-day forward 
timeframe, the 10-day threshold will provide very little additional 
benefits in existing RTO/ISO markets. Accordingly, the 10-day threshold 
will not apply to internal transactions or internal flows associated 
with through-and-out transactions in RTOs/ISOs. However, given that 
RTOs/ISOs generally use the pro forma OATT transmission service model 
for movement of electricity into/out of their service territories, the 
10-day threshold requirement will apply to RTOs/ISOs' evaluation or 
determination of availability of transmission service at the seams of 
RTO/ISO service territories, in order to improve the accuracy of 
transmission line ratings and ensure just and reasonable wholesale 
rates.
b. Role of the Transmission Owner and Transmission Provider in AAR 
Implementation
i. NOPR Proposal
    135. In proposing AAR implementation in the pro forma OATT, the 
Commission proposed for transmission providers--not transmission 
owners--to implement AARs because transmission providers--not 
transmission owners--must have an OATT.\317\
---------------------------------------------------------------------------

    \317\ NOPR, 173 FERC ] 61,165 at P 84.
---------------------------------------------------------------------------

ii. Comments
    136. Several commenters clarify that transmission owners, not 
transmission providers, calculate transmission line ratings.\318\ For 
example, MISO states that its formational documents reflect, and have 
codified, the responsibility of transmission owners to calculate 
facility ratings, not MISO.\319\ MISO Transmission Owners explain that 
Reliability Standard FAC-008-5 requires transmission owners to have ``a 
documented methodology for determining facility ratings of its solely 
and jointly owned Facilities'' based on the electrical characteristics 
of the transmission equipment or other industry standard.\320\ Southern 
Company states that the MOD suite of NERC Reliability Standards 
governing TTC/ATC calculations requires transmission line ratings as 
provided by transmission owners.\321\ Similarly, ISO-NE explains that 
its Transmission Operating Agreement requires its participating 
transmission owners to establish transmission line ratings for each 
transmission facility.\322\ Additionally, NYISO states that in the New 
York Control Area, the transmission owners are responsible for 
developing transmission line ratings and providing the element ratings 
directly to NYISO. In turn, according to NYISO, NYISO determines the 
most limiting element, which sets the applicable facility rating.\323\
---------------------------------------------------------------------------

    \318\ MISO Comments at 27; Vistra Comments at 3-4; TAPS Comments 
at 13-14; Southern Company Comments at 6; EEI Comments at 2-4; MISO 
Transmission Owners at 29; EEI Comments at 2-4.
    \319\ MISO Comments at 27.
    \320\ MISO Transmission Owners at 29.
    \321\ Southern Company Comments at 3, 6.
    \322\ ISO-NE Comments at 6.
    \323\ NYISO Comments at 3.

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[[Page 2267]]

    137. Because of these differing transmission owner and transmission 
provider roles and responsibilities, these commenters request that the 
Commission recognize and make these differing roles explicit in any 
final rule.\324\ Some recommend further Commission action to ensure 
transmission owners have an obligation to implement the AAR 
requirements in proposed pro forma OATT Attachment M. For example, 
Vistra encourages the Commission to modify its regulations to create a 
compliance obligation for each transmission owner to provide RTOs/ISOs 
all information necessary to implement proposed pro forma OATT 
Attachment M.\325\ Similarly, TAPS requests that the Commission clarify 
that: (1) RTOs/ISOs have the authority to require transmission owners 
to provide the information they will need to implement AARs; or (2) 
transmission owners within RTOs/ISOs must provide the information RTOs/
ISOs will need to implement AARs to the relevant RTO/ISO.\326\ 
Additionally, TAPS argues that in order to achieve efficient and 
consistent application of AARs, the Commission should direct RTOs/ISOs 
to use, or at minimum accommodate the use of, ``look-up tables.'' \327\ 
TAPS explains that, using the ``look-up table'' approach will limit the 
obligation to continuously monitor weather reports to recalculate AARs 
and communicate those transmission line ratings to the RTO/ISO on an 
hourly basis.\328\
---------------------------------------------------------------------------

    \324\ MISO Comments at 27; Vistra Comments at 3-4; TAPS Comments 
at 13-14; Southern Company Comments at 6; EEI Comments at 2-4.
    \325\ Vistra Comments at 3-4.
    \326\ TAPS Comments at 14.
    \327\ Id. at 8. TAPS states that, for each of their transmission 
facilities, transmission owners should be required to provide RTOs/
ISOs with a table showing their temperature-adjusted rating for a 
pre-established set of ambient air temperatures.
    \328\ Id. at 8-10.
---------------------------------------------------------------------------

    138. Noting the applicability of the pro forma OATT to transmission 
providers and that transmission owners and transmission providers are 
different in RTO/ISOs, Exelon comments on the phrasing ``is 
calculated'' in the AAR definition, explaining that, while it largely 
supports the proposed AAR definition, it does not ``calculate'' 
transmission line ratings hourly. Exelon states that it calculates 64 
different transmission line rating cases (for nine temperatures sets, 
across normal, long-term emergency, short-term emergency, emergency 
load dump, and for both day and night), and then references the 
relevant existing calculations in a ``look-up table'' through its 
Inter-Control Center Communications Protocol signal. Exelon proposes to 
refine the AAR term to: ``a transmission line rating that reflects the 
appropriate temperature-adjusted rating for a facility based on an up-
to-date forecast of ambient air temperatures across the time period to 
which the rating applies.'' \329\
---------------------------------------------------------------------------

    \329\ Exelon Comments at 11-12.
---------------------------------------------------------------------------

    139. Finally, CAISO argues that RTOs/ISOs and their stakeholders 
will have to answer many questions in developing tariff provisions for 
using hourly transmission line ratings. Several of these questions 
relate to AAR implementation timelines, including the time hourly 
transmission line ratings must be submitted by the transmission owners 
to RTOs/ISOs and the time period that transmission owners will have to 
update hourly transmission line ratings for use in real-time markets 
after day-ahead results are published.\330\ As an example, BPA explains 
that its dynamically established TTC calculations are based on 
schedules submitted 20 minutes before the operating hour.\331\
---------------------------------------------------------------------------

    \330\ CAISO Comments at 12-13.
    \331\ BPA Comments at 5.
---------------------------------------------------------------------------

iii. Commission Determination
    140. We clarify that transmission owners, not transmission 
providers, are responsible for calculating transmission line ratings. 
This responsibility is codified in the NERC Reliability Standards, as 
well as in RTO/ISO foundational documents.\332\ Nothing in this final 
rule changes that responsibility. In the non-RTO/ISO regions, this 
detail is generally not a concern because the transmission provider is 
usually the transmission owner. However, in the RTO/ISO regions, there 
is a distinction between transmission owners and transmission 
providers. Thus, in order to comply with this final rule, RTOs/ISOs--
the transmission provider with the OATT on file--will need to rely on 
their member transmission owners to calculate transmission line ratings 
and provide them to the RTO/ISO.\333\
---------------------------------------------------------------------------

    \332\ See, e.g., Reliability Standards FAC-008-5, Requirement R3 
and FAC-008-5, Requirement R6.
    \333\ We note that, as discussed below, in RTO/ISO regions, in 
addition to AARs, transmission owners will be required to calculate 
and provide other transmission line ratings to the RTO/ISO, 
including seasonal line ratings and emergency ratings. Moreover, in 
RTO/ISO regions, transmission owners will be required to provide to 
the RTO/ISO the list of transmission lines which have been exempted 
from the AAR requirement (under the ``Exceptions'' paragraph of pro 
forma OATT Attachment M) or temporary alternate ratings (under the 
``System Reliability'' section of pro forma OATT Attachment M).
---------------------------------------------------------------------------

    141. In response to concerns about the responsibility for 
calculating transmission line ratings in RTOs/ISOs, we clarify that we 
expect RTOs/ISOs to require their member transmission owners to make 
timely calculations and determinations as required for transmission 
line ratings, and to provide them to the RTO/ISO.\334\ Where the 
transmission provider is not the transmission owner (e.g., RTOs/ISOs), 
we require the transmission provider to explain in its compliance 
filing, as part of its implementation of the new pro forma OATT 
Attachment M, through what mechanism (tariff, membership agreement, 
etc.) the transmission owner(s) will have the obligation for making and 
communicating to the transmission provider the timely calculations and 
determinations related to transmission line ratings (including the 
exercise of any discretion in calculations or application of 
exceptions).
---------------------------------------------------------------------------

    \334\ See, e.g., MISO, MISO Rate Schedules, MISO Transmission 
Owner Agreement, art. 4, Sec.  II.A Providing Information (30.0.0) 
(``Each Owner and User shall provide such information to [MISO] as 
is necessary for [MISO] to perform its obligations under this 
Agreement and the Tariff.''); SPP, Governing Documents Tariff, 
Membership Agreement, Sec.  3.5 Providing Information (0.0.0) 
(``Member shall provide such information to SPP as is necessary for 
SPP to perform its obligations under this Agreement and the OATT, 
and for planning and operational purposes.''); PJM, Rate Schedules, 
Sec.  4.11 Transmission Facility Ratings (0.0.0) (``All Parties 
shall regularly update and verify Transmission Facility ratings, 
subject to review and approval by PJM, in accordance with the 
following procedures and the procedures in the PJM Manuals . . . 
.''); ISO-NE, ISO New England Inc. Agreements and Contracts, 
Transmission Operating Agreement, Sec. Sec.  3.02(a)(ii) (5.0.0) 
(stating that ISO-NE shall ``determine Operating Limits based on 
forecasted or real-time system conditions and in accordance with the 
facility ratings established by the PTOs in collaboration with the 
ISO pursuant to Section 3.06''), 3.06(a)(v) (5.0.0) (stating that 
the transmission owner shall: ``(v) Collaborate with the ISO with 
respect to: (A) The development of Rating Procedures, (B) the 
establishment of ratings for each PTO's New Transmission Facilities; 
(C) the establishment of ratings for each PTO's Acquired 
Transmission Facilities that do not have an existing rating as of 
the Operations Date, and (D) the establishment of any changes to 
existing ratings for Transmission Facilities in effect as of the 
Operations Date''); CAISO, CAISO eTariff, Transmission Control 
Agreement, Sec.  4.2 (0.0.0) (stating that facility ratings are 
required CAISO's database of all facilities under the CAISO's 
control and that transmission owners are responsible for providing 
updates to that database when there is a change in ratings, which 
CAISO reviews).
---------------------------------------------------------------------------

    142. In response to Exelon's concerns about the proposed AAR 
definition,\335\ we clarify that hourly (or more frequent) querying of 
``look-up tables'' or similar pre-calculated AAR databases will satisfy 
the requirement that AARs be calculated at least each hour. While we 
expect transmission owners to calculate transmission line ratings, 
given the difference between transmission owners and transmission 
providers in RTOs/ISOs, we require RTOs/ISOs on compliance to propose 
and justify a

[[Page 2268]]

methodology for AAR implementation, delineating the expected roles 
between transmission owners and transmission provider. In doing so, we 
encourage RTO/ISO transmission owners to coordinate implementation 
methodologies and promote implementation consistency to the greatest 
extent possible within an RTO/ISO service territory. However, in 
response to comments from TAPS that the Commission should require use 
of a ``look-up table'' approach, or at least require that approach be 
an option,\336\ we decline to require a specific AAR implementation 
methodology, noting regional software and procedural differences.
---------------------------------------------------------------------------

    \335\ Exelon Comments at 11-12.
    \336\ TAPS Comments at 7-10.
---------------------------------------------------------------------------

    143. In response to requests for clarification from CAISO, we 
decline to require in this final rule a specific timeline by which AARs 
will need to be calculated or submitted to the transmission provider 
(either in the context of the day-ahead and real-time markets in RTOs/
ISOs, or in terms of how far in advance of an operating hour an AAR 
should be calculated in a bilateral market).\337\ However, we note that 
the AAR definition we adopt in this final rule requires that AARs 
``[r]eflect[] an up-to-date [emphasis added] forecast of ambient air 
temperature across the time period to which the rating applies,'' by 
which we mean that new forecast data should be incorporated into AAR 
calculations as close to real time as reasonably possible given the 
timelines needed to obtain forecast data and perform the AAR 
calculation, as well as any other steps needed for validation, 
communication, or implementation of AARs.\338\ Furthermore, 
transmission providers must explain their timelines as part of their 
compliance filings. We recognize that transmission providers already 
manage similar timing issues with respect to load forecasts, forecasts 
for renewable energy production, and generation bid deadlines, and it 
may be that deadlines for AAR calculation/submission are not 
significantly different from existing deadlines for submission of 
updates to generation supply offers and load.
---------------------------------------------------------------------------

    \337\ We note that in some instances RTOs/ISOs may propose (as 
we understand PJM does now for its AARs) to have the RTO/ISO select 
AARs based on temperature forecasts and pre-calculated AAR tables/
databases. In such cases, it may not be (as CAISO's comments 
suggest) that transmission owners will be sending entire sets of 
AARs to RTOs/ISOs every time they are calculated.
    \338\ Pro Forma OATT attach. M, AAR Definition.
---------------------------------------------------------------------------

c. Solar Heating in AAR Calculations
i. NOPR Proposal
    144. In the NOPR, the Commission proposed to require AARs that 
reflect up-to-date forecasts of ambient air temperature, but noted that 
AARs could possibly incorporate other forecasted inputs.\339\ As an 
example of other inputs, the Commission pointed to PJM's implementation 
of ``day and night ambient air temperature tables, where the night 
ambient air temperature table assumes zero solar irradiance.'' \340\ 
The Commission also sought comment on whether to require transmission 
providers to implement DLRs, rather than only AARs, noting that DLRs 
can incorporate solar heating intensity, among other ambient 
conditions, to calculate the amount of transfer capability of a given 
transmission line in near real time.\341\
---------------------------------------------------------------------------

    \339\ NOPR, 173 FERC ] 61,165 at P 23.
    \340\ Id. P 23 n.40; see also id. P 21 (explaining that 
different types of ambient weather assumptions can be incorporated 
into transmission line ratings, including updated air temperature, 
solar irradiance, and wind speed, among others).
    \341\ Id. PP 25-26, 43.
---------------------------------------------------------------------------

ii. Comments
    145. Several commenters discuss the incorporation of solar heating 
into transmission line ratings. For example, Vistra suggests that, 
instead of requiring full DLRs, the Commission instead adopt a ``middle 
ground'' of requiring AARs that incorporate consideration of 
predictable solar heating (at least considering daytime/nighttime 
hours, similar to PJM's existing implementation of AARs).\342\ Potomac 
Economics and Vistra contend that such a requirement would not 
necessitate sophisticated monitoring or forecasting, and instead would 
produce significant benefits with minimal cost.\343\ R Street 
Institute, PG&E, Indicated PJM Transmission Owners, Dominion, and 
Potomac Economics also support incorporating predictable daytime/
nighttime solar heating into AARs, with Dominion and Indicated PJM 
Transmission Owners noting that this is already the practice in 
PJM.\344\ Entergy, without taking a position on whether it would be 
appropriate for the Commission to require separately calculated daytime 
and nighttime ratings, states that the shade of night provides an 
additional 5% to the transmission line's transmission line 
ratings.\345\ PG&E states that it supports separately calculated 
daytime and nighttime ratings and indicates that its research from 
PJM's posted transmission line ratings shows that at least 14% of PJM's 
transmission line ratings would increase by 10% by considering solar 
heating.\346\ Potomac Economics estimates that considering daytime/
nighttime could increase thermal transmission line ratings on average 
by 11% during nighttime hours and the potential benefits would be 
approximately $30 million per year in MISO alone.\347\
---------------------------------------------------------------------------

    \342\ Vistra Comments at 4-5.
    \343\ Id. at 4-5; Potomac Economics Comments at 14-15.
    \344\ R Street Institute Comments at 3; PG&E Comments at 11-12; 
Indicated PJM Transmission Owner Comments at 8-9; Dominion Comments 
at 8; Potomac Economics Comments at 14-15.
    \345\ Entergy Comments at 8.
    \346\ PG&E Comments at 11.
    \347\ Potomac Economics Comments at 14-15.
---------------------------------------------------------------------------

    146. Vistra points out that solar heating varies in several ways: 
Between daytime and nighttime (with sunrise/sunset times and day length 
varying significantly across the year), across the hours during the day 
(varying--under worst-case, clear-sky assumptions--from close to zero 
just after and before sunrise and sunset, respectively, to a daily mid-
day peak), and across the days of the year (with higher mid-day peaks 
in the summer and lower peaks in the winter).\348\ Vistra and PG&E both 
suggest that the Commission consider requiring regular updates to 
sunrise/sunset times, with Vistra discussing possible daily or seasonal 
updates, and PG&E discussing possible monthly updates.\349\ 
Furthermore, while Vistra recommends that the Commission at the very 
least require separate daytime and nighttime AARs, Vistra also provides 
data for how solar heating varies significantly across the day, and 
discusses how more granular solar forecasting might reflect these solar 
variations.\350\
---------------------------------------------------------------------------

    \348\ Vistra Comments at 4-6; see also PG&E Comments at 11-12.
    \349\ Vistra Comments at 5; PG&E Comments at 12.
    \350\ Vistra Comments at 4-5.
---------------------------------------------------------------------------

iii. Commission Determination
    147. Upon consideration of the comments received in response to the 
NOPR, we require transmission providers to incorporate solar heating 
into AARs by implementing separate AARs for daytime and nighttime 
periods. Specifically, we require transmission providers to reflect the 
lack of solar heating in the technical assumptions for nighttime AARs. 
As noted by Dominion and Indicated PJM Transmission Owners, 
incorporating solar heating into AARs is consistent with PJM's existing 
AAR implementation.\351\ Absent this requirement for daytime/nighttime

[[Page 2269]]

AARs, AARs would assume the worst-case solar heating assumptions in 
every hour, even at night when there is no solar heating of 
transmission lines at all.
---------------------------------------------------------------------------

    \351\ Dominion Comments at 7-8; Indicated PJM Transmission 
Owners Comments at 7.
---------------------------------------------------------------------------

    148. The consideration of daytime/nighttime solar heating in the 
AARs used by transmission providers will further the Commission's goal 
of ensuring more accurate transmission line ratings, which result in 
just and reasonable wholesale rates. Furthermore, as commenters note, 
the improvements to the accuracy of transmission line ratings that will 
result from adopting a daytime/nighttime AAR requirement can yield 
significant economic benefits at minimal cost.\352\
---------------------------------------------------------------------------

    \352\ Vistra Comments at 4-5; Potomac Economics Comments at 14-
15.
---------------------------------------------------------------------------

    149. We agree with commenters that sunrise/sunset times should be 
updated periodically to ensure the accuracy of both daytime and 
nighttime ratings. Specifically, we clarify that in order to comply 
with the requirement in pro forma OATT Attachment M for AARs to reflect 
the absence of solar heating during nighttime periods, transmission 
providers must update the sunrise and sunset times used to calculate 
their AARs at least monthly, if not more frequently. We find that among 
the daily, monthly, and seasonal timeframes suggested by commenters, 
the requirement to update sunrise/sunset times on a monthly basis 
strikes an appropriate balance between achieving the greatest benefits 
of AAR implementation and not imposing an unreasonable burden on 
transmission providers. Given the speed at which sunrise and sunset 
times change in many areas of the country during certain times of the 
year, monthly updates will result in significantly more accuracy in 
transmission line ratings and capture significantly greater value than 
seasonal updates. Because sunrise/sunset times can be easily calculated 
with precision based on location and day of the year,\353\ and because 
we expect AAR implementation to be largely automated, we do not expect 
monthly updates to sunrise/sunset times to impose a significant 
additional implementation burden relative to seasonal updates. Nothing 
in this final rule would prevent a transmission provider from updating 
its sunrise/sunset times more frequently than monthly and we encourage 
transmission providers to do so.\354\
---------------------------------------------------------------------------

    \353\ See, e.g., National Oceanic and Atmospheric 
Administration, Global Monitoring Division, General Solar Position 
Calculations, https://gml.noaa.gov/grad/solcalc/solareqns.PDF 
(providing formulas for calculating sunrise/sunset times based on 
latitude, longitude, and day of the year).
    \354\ We note that PJM currently updates its sunrise/sunset 
times more frequently than monthly in its day/night AAR 
implementation.
---------------------------------------------------------------------------

    150. Vistra correctly points out that, in addition to sunrise/
sunset times, solar heating also varies across the days of the year and 
the hours of the day. However, again, to maintain a balance of benefits 
and burdens, we decline to require regular updates to mid-day peak 
solar heating to account for differences across days of the year. As 
such, transmission providers may use maximum annual assumptions for 
solar heating when determining daytime AARs. Furthermore, to balance 
benefits and burdens, we decline to require more granularity (e.g., 
hourly forecasts) in solar heating assumptions and only require 
daytime/nighttime consideration. We note, however, that nothing in this 
final rule would prohibit a transmission provider that wants to 
voluntarily implement regular updates to peak mid-day solar heating, or 
to voluntarily implement hourly forecasts for solar heating, from doing 
so. We further note that peak or hourly daytime solar heating (under 
worst-case clear-sky assumptions) can be accurately computed based on 
location using equations such as those presented in IEEE (Institute of 
Electrical and Electronics Engineers) Standard 738.\355\
---------------------------------------------------------------------------

    \355\ Institute of Electrical and Electronics Engineers, IEEE 
Standard for Calculating the Current-Temperature Relationship of 
Bare Overhead Conductors 18-20, IEEE Std 738-2012 Cor 1-2013 (2013) 
(IEEE 738).
---------------------------------------------------------------------------

3. Other AAR Implementation Issues
a. Reliability Unit Commitment Processes
i. NOPR Proposal
    151. In the NOPR, the Commission proposed that RTOs/ISOs comply 
with the AAR requirements by revising their OATTs to implement AARs 
within their SCED and SCUC models (and in any relevant related models) 
in both the day-ahead and real-time markets and in any intra-day RUC 
processes.\356\
---------------------------------------------------------------------------

    \356\ NOPR, 173 FERC ] 61,165 at P 91.
---------------------------------------------------------------------------

ii. Comments
    152. CAISO requests clarification on whether hourly transmission 
line ratings should be constant in RUC processes.\357\
---------------------------------------------------------------------------

    \357\ CAISO Comments at 12-13.
---------------------------------------------------------------------------

iii. Commission Determination
    153. In response to CAISO, we clarify that transmission providers 
should propose on compliance to use updated AARs as part of any market 
process associated with the day-ahead and real-time markets (including 
RUC, as well as any look-ahead commitment processes or other such 
processes). In the event an RTO/ISO believes that AARs should not be 
used as part of any market process associated with the day-ahead and 
real-time markets (or that updated AARs should not be required for any 
market process), it should propose and justify such deviations on 
compliance.
b. Time Resolution and Calculation Frequency of AAR Requirements
i. NOPR Proposal
    154. In defining AARs, the Commission proposed to require that AARs 
be calculated at least each hour, if not more frequently, and for AARs 
to apply to a time period of not greater than one hour.\358\
---------------------------------------------------------------------------

    \358\ NOPR, 173 FERC ] 61,165 at P 95.
---------------------------------------------------------------------------

ii. Comments
    155. Many state agencies, supply and load representatives, 
renewable energy advocates, and independent experts support the 
proposed AAR requirements overall, which includes the proposed time 
resolution or calculation frequency.\359\ RTOs/ISOs are mixed in 
whether they take a position and generally discuss their ability to 
accept AARs calculated hourly. For example, while not taking a position 
on the appropriateness of this part of the NOPR proposal, MISO explains 
that its EMS and SCED are capable of receiving and leveraging AARs 
provided by their transmission owners at least hourly.\360\
---------------------------------------------------------------------------

    \359\ EPSA Comments at 2; Clean Energy Parties Comments at 2-3; 
R Street Institute Comments at 2-3; TAPS Comments at 1-3; ACORE 
Comments at 3; ACPA/SEIA Comments at 7; OMS Comments at 2; New 
England State Agencies Comments at 10; Vistra Comments at 2-3.
    \360\ MISO Comments at 12.
---------------------------------------------------------------------------

    156. CAISO explains that its transmission owners can submit AARs, 
but that the fundamental challenge with using AARs is timely 
communication of forecasted transmission line ratings. According to 
CAISO, participating transmission owners currently submit AARs as an 
equipment rating change through CAISO's outage management system 
(webOMS).\361\ CAISO further states that using hourly adjusted 
transmission line ratings for transmission lines across the 24-hour 
horizon of a trading day will necessarily and significantly increase 
the complexity of CAISO's day-ahead optimization processes.\362\ In 
addition, CAISO contends that hourly transmission line ratings in real-
time markets may drive uplift costs by causing variances between total 
transfer

[[Page 2270]]

capability used in each of CAISO's commitment and dispatch processes. 
In addition, CAISO asserts that transmission line rating changes over 
the market run's look-ahead period can generate inefficient outcomes 
through deviations from day-ahead schedules.\363\
---------------------------------------------------------------------------

    \361\ CAISO Comments at 4.
    \362\ Id. at 9-10.
    \363\ Id. at 10-11.
---------------------------------------------------------------------------

    157. Similarly, NYISO cautions against requiring hourly updates to 
transmission line ratings if they are not already used by RTOs/
ISOs.\364\ NYISO explains that introducing hourly transmission line 
ratings could result in divergences from the day-ahead schedule, 
creating uplift or potential reliability risks, if hourly transmission 
line ratings cause a transmission line rating to decline.\365\ On 
hourly updates to AARs, NYISO notes that its market software looks 
ahead, including a 24-hour day-ahead optimization and multi-period 
commitment for the real-time market.\366\ NYTOs note that NYISO and 
NYTOs can apply AARs and DLRs to congested transmission lines currently 
in real time to increase transmission line ratings.\367\
---------------------------------------------------------------------------

    \364\ NYISO Comments at 4.
    \365\ Id. at 4-5.
    \366\ Id. at 13.
    \367\ NYTOs Comments at 4.
---------------------------------------------------------------------------

    158. ISO-NE states that it allows for short-term changes to 
transmission line ratings, though not at an hourly level.\368\ ISO-NE 
further states that its coordinated transaction scheduling with NYISO 
runs every 15 minutes and therefore a shorter interval would have to be 
considered.\369\
---------------------------------------------------------------------------

    \368\ ISO-NE Comments at 6-7.
    \369\ Id. at 9.
---------------------------------------------------------------------------

    159. While PJM supports the adoption of AARs, it opposes the 
requirements that a transmission line rating apply to a period not 
greater than one hour and that transmission line ratings be updated 
hourly. PJM states that the key factor for determining the transmission 
line rating is the temperature and, as a result, the primary event that 
triggers a change in AARs is the ambient air temperature. PJM states 
that, in implementing AARs, it continuously monitors temperatures and 
updates transmission line ratings for temperature fluctuations in 
accordance with the transmission owners' look-up table, so there is no 
benefit to updating the AARs hourly if no temperature change has 
occurred.\370\ Relatedly, PJM and Duke Energy state that the proposed 
requirements in the NOPR that transmission line ratings be updated 
hourly could harm operations.\371\ This is because, according to PJM, a 
significant temperature change could occur between required hourly 
updates and, if a transmission operator is not continuously monitoring 
ambient air temperature, an incorrect transmission line rating would be 
effective from the time of the temperature change until the next 
mandated hourly update.\372\ PJM states that these temporal 
requirements simply add an administrative burden without providing 
additional benefits.\373\ PJM requests that the Commission refrain from 
requiring transmission providers to apply AARs in hourly intervals but 
rather require them to be continuously monitored with changes triggered 
by temperature changes and the other relevant factors in the look-up 
tables.\374\
---------------------------------------------------------------------------

    \370\ PJM Comments at 4-5.
    \371\ Id. at 5; Duke Energy Comments at 8.
    \372\ PJM Comments at 5.
    \373\ Id. at 2 n.5.
    \374\ Id. at 6.
---------------------------------------------------------------------------

    160. Many transmission owners also request flexibility on the 
proposed requirement for AARs to be calculated ``at least each hour.'' 
\375\ ITC asks that the Commission instead only require daily AAR 
updates and notes that this is the prevailing practice for transmission 
owners using AARs in MISO.\376\ MISO Transmission Owners also request 
flexibility to implement daily rather than hourly AARs.\377\ Indicated 
PJM Transmission Owners argue against requiring hourly AAR 
calculations.\378\ Indicated PJM Transmission Owners explain that PJM 
adjusts transmission line ratings over the day as temperatures change, 
but state that there is little benefit to hourly verification of 
temperature changes because transmission line ratings in PJM do not 
typically change hourly. Similarly, EEI argues for a requirement for 
daily AAR updates for real-time operations.\379\
---------------------------------------------------------------------------

    \375\ ITC Comments at 9; MISO Transmission Owners Comments at 
24; EEI Comments at 12; Duke Energy Comments at 10.
    \376\ ITC Comments at 9.
    \377\ MISO Transmission Owners Comments at 24.
    \378\ AEP Comments at 6-7; Dominion Comments at 3; Indicated PJM 
Transmission Owners Comments at 7-9.
    \379\ EEI Comments at 12; PacifiCorp Comments at 2; BPA Comments 
at 3; WAPA Comments at 6-7.
---------------------------------------------------------------------------

    161. In contrast, Entergy explains that it automatically updates 
AARs every hour for the approximately 1,000 facilities for which it 
calculates AARs, and this information is automatically updated hourly 
in Entergy's Real Time Contingency Analysis so the operator does not 
have to look at charts.\380\ Exelon also contends that an hourly 
transmission line ratings check would not be overly burdensome and 
instead could help to prevent overloading a transmission line.\381\ 
Exelon also urges the Commission to provide sufficient flexibility to 
ensure transmission line ratings can change intra-hourly.\382\ 
Moreover, Exelon comments that it believes that the Commission's 
proposed requirements are sufficiently flexible to accommodate PJM's 
current approach.\383\
---------------------------------------------------------------------------

    \380\ Entergy Comments at 3.
    \381\ Exelon Comments at 9-10.
    \382\ Id.
    \383\ Id. at 9.
---------------------------------------------------------------------------

iii. Commission Determination
    162. We adopt the Commission's proposal in the NOPR to require the 
calculation of AARs ``at least each hour, if not more frequently'' and 
the requirement that AARs ``appl[y] to a time period of not greater 
than one hour.'' \384\
---------------------------------------------------------------------------

    \384\ NOPR, 173 FERC ] 61,165 at P 3 n.3.
---------------------------------------------------------------------------

    163. With respect to calculation frequency, we believe that 
performing AAR calculations at least hourly appropriately balances 
requiring updates at a frequency that captures meaningful changes in 
ambient air temperature forecasts, and not overburdening transmission 
providers. In response to concerns that the requirement for hourly 
calculations may be unduly burdensome because temperature forecasts do 
not always fluctuate hour by hour, we recognize that in some hours 
forecasts for temperatures do not change, primarily because weather 
services do not always have updated forecasted values for every 
location each hour. However, it is not known exactly when such 
forecasted values will be updated, and, therefore, our requirement to 
calculate AARs hourly appropriately requires transmission providers to 
check for forecast updates and apply any updates that are available. We 
believe that the requirement to calculate AARs hourly ensures that any 
such publication of forecast updates are incorporated into AARs in a 
reasonable timeframe.\385\ If we were to instead require such 
calculations on a longer time period (e.g., every eight hours), then 
there would be some instances when published available weather forecast 
updates would not be incorporated into AARs in time to accurately 
reflect the transmission line's true transfer capability. Moreover, we 
expect this process for AAR implementation to be largely automated, 
with computer systems querying or receiving updated forecasts and 
processing any such data

[[Page 2271]]

into updated AARs, such that calculating AARs hourly should not be 
significantly more burdensome than calculating AARs daily. We agree 
with Exelon that AAR calculations at least hourly are likely to be an 
important tool used to prevent any transmission overload that might 
occur as a result of a sudden, unexpected temperature increase.\386\ We 
add that this requirement does not preclude intra-hour updates.
---------------------------------------------------------------------------

    \385\ For example, we understand that the NBM forecast (which is 
a blend of distinct constituent forecasts) has updates published at 
least every hour, but the constituent forecasts are typically 
updated only three times per day. Exactly when the constituent 
forecasts will be updated is not precise, such that an update to any 
forecasted value might change in any hour.
    \386\ Exelon Comments at 9-10.
---------------------------------------------------------------------------

    164. We acknowledge, in response to comments by CAISO and NYISO, 
that within RTOs/ISOs there will be times when AARs produce real-time 
transmission line ratings that diverge from what was previously 
calculated in the day-ahead market (based on earlier forecasts), and 
that this may result in operating considerations and uplift costs. 
However, we are not persuaded that such considerations or costs 
outweigh the benefits of updating real-time transmission line ratings 
discussed above. Further, updating transmission line ratings closer to 
real time will help ensure that the most accurate transmission line 
ratings are used in the real-time energy market and, in turn, tend to 
reduce costs and promote reliable operations. Commenters seem to argue 
that if the weather conditions unexpectedly change, such that 
temperatures are significantly lower and significantly more transfer 
capability is able to be used in real time compared to day ahead, the 
markets should keep such transfer capability in reserve in order to 
minimize uplift. We disagree that a concern about potential uplift 
should result in transfer capability being withheld from the real-time 
energy market with associated limits on the economic benefits of using 
AARs. Further, we do not believe that any operating considerations 
associated with updating transmission line ratings in real time will 
compromise reliable operations. As PJM states, AARs are already 
employed in PJM in both the day-ahead and real-time markets and, in its 
experience, AARs increase operational flexibility, promote a more 
efficient use of the transmission system, and result in more reliable 
system dispatch and cost-effective market operations.\387\
---------------------------------------------------------------------------

    \387\ PJM Comments at 2.
---------------------------------------------------------------------------

    165. One of the reasons that substantial uplift is sometimes 
considered problematic is that it may be evidence that the market is 
not accurately considering operating constraints, which gives rise to 
out-of-market actions and distorts short-term and long-term price 
signals.\388\ While we acknowledge the potential for uplift in certain 
situations, the reason for incurring uplift here is very different. 
Updating transmission line ratings in real time will result in more 
accurate prices that reflect actual real-time operating constraints. 
Accordingly, the potential for the generation of uplift through our AAR 
requirements would not be evidence of market design concerns or 
inaccurate price signals.
---------------------------------------------------------------------------

    \388\ Uplift Cost Allocation and Transparency in Mkts. Operated 
by Reg'l Transmission Orgs. and Indep. Sys. Operators, Order No. 
844, 83 FR 18134 (Apr. 25, 2018), 163 FERC ] 61,041, at P 3 (2018).
---------------------------------------------------------------------------

    166. As discussed above, we believe that, under the AAR 
requirements adopted in this final rule, transmission providers will 
implement AARs with sufficient forecast margins in forward periods such 
that instances of reductions in transfer capability in real time and 
the related operational challenges will be infrequent. Accordingly, we 
anticipate that transfer capability will typically be freed up as 
forecasts become more certain (and require smaller forecast margins) 
from forward periods to actual operation, which will typically result 
in additional transmission being made available as we approach real 
time, and this will create some uplift. But we find this is the result 
of the policies that are needed to ensure transmission line ratings are 
sufficiently accurate to produce just and reasonable wholesale rates, 
and that any resulting uplift is, therefore, appropriate. Additionally, 
however, we acknowledge that transmission providers might also 
implement unreasonably high ambient air temperature forecast margins. 
In such instances, such unreasonably high forecast margins would need 
to be adjusted to ensure transmission line ratings are accurate.
    167. We clarify that this final rule does not prohibit transmission 
providers from utilizing AARs that are calculated on a more frequent 
basis than hourly. Relatedly, in response to comments from PJM, we 
clarify that nothing in this final rule prevents a transmission 
provider from utilizing a transmission line rating calculated in 
between whatever standard AAR calculation period is established.
    168. Turning to the hourly resolution (as opposed to the hourly 
frequency of calculation) of AARs, we adopt the NOPR proposal to 
require that AARs ``appl[y] to a time period of not greater than one 
hour'' because we find such a policy strikes an appropriate balance 
between providing sufficient granularity to transmission line ratings 
to reflect meaningful predictable changes in ambient air temperature 
across each day, and not overburdening transmission providers.\389\ 
These changes are different from changes in ambient air temperatures 
discussed above, which are changes in forecasts due to improved 
information as a time period moves closer to real time as time 
advances.
---------------------------------------------------------------------------

    \389\ Pro Forma OATT attach. M, AAR Definition.
---------------------------------------------------------------------------

    169. We find that ambient air temperatures typically vary 
sufficiently across the day to produce meaningful differences in hourly 
transmission line ratings. For example, we expect temperatures during 
morning or evening hours to typically be significantly different than 
the noon temperature. Recognizing such temperature differences through 
transmission line ratings may be particularly important, since 
increasingly systems are being challenged during such morning or 
evening hours due to ramp or peak net load challenges. We find that 
hourly AAR calculations will create important additional operational 
flexibility for operators and more accurate transmission line ratings. 
And because we expect the AAR process to be largely automated, we do 
not believe that the requirement for hourly AARs will be significantly 
more burdensome than a less granular requirement (e.g., a requirement 
that AARs apply to a time period of not greater than one day). In any 
event, we clarify that this final rule does not preclude a transmission 
provider from implementing AARs on a more granular basis than hourly, 
such as the 15-minute basis suggested by ISO-NE with respect to its 
coordinated transaction scheduling.
c. AAR Coordination
i. Comments
    170. Several commenters argue that further consideration is needed 
on AAR implementation in certain circumstances.\390\ For example, while 
not supporting or opposing an AAR mandate, NERC stresses the importance 
of reliability, explaining that reliability of the transmission system 
depends upon the proper coordination of transmission line ratings,\391\ 
and states that special attention must be paid to reliability 
considerations in the implementation of any reforms in this 
proceeding.\392\ Specifically, NERC notes that the Commission should 
consider whether to require transmission

[[Page 2272]]

providers to coordinate AAR implementation methods since temperature 
readings and methodologies may differ on tie lines, and which 
transmission line rating should be used in the event of a disagreement 
among entities receiving transmission line ratings or 
methodologies.\393\
---------------------------------------------------------------------------

    \390\ NERC Comments at 6-7; EEI Comments at 14-15; NYTOs 
Comments at 7; CAISO Comments at 12-13.
    \391\ NERC Comments at 4.
    \392\ Id.
    \393\ Id. at 6-7.
---------------------------------------------------------------------------

    171. EEI asserts that the NOPR proposal was unclear about how AARs 
on transmission lines across seams should be determined, where 
transmission line ratings could be subject to assumptions from two 
different transmission providers, and how AAR compliance could be 
determined for non-jurisdictional transmission facilities. EEI urges 
flexibility on seams issues and for the Commission to enforce 
reciprocity conditions for non-jurisdictional entities, should the 
Commission require targeted AAR implementation.\394\ IID also 
encourages the Commission to consider seams issues that may need to be 
addressed if AARs are different among neighboring utilities.\395\ MISO 
Transmission Owners similarly state that ATC calculations on joint 
flowgates and tie lines between RTOs/ISOs will require coordination 
among all parties each time a transmission line rating changes, 
increasing the level of communication necessary. According to MISO 
Transmission Owners, along these joint flowgates and tie lines, 
transmission owners and RTOs/ISOs will need to decide which forecast 
will govern and whether to use multiple weather forecasts.\396\
---------------------------------------------------------------------------

    \394\ EEI Comments at 14-15.
    \395\ IID Comments at 6-7.
    \396\ MISO Transmission Owners Comments at 32-33.
---------------------------------------------------------------------------

ii. Commission Determination
    172. We agree with NERC's comments stressing the importance of 
reliability and reiterate that system safety and reliability are 
paramount to the requirements for transmission line ratings that we 
adopt in this final rule. We agree with NERC and other commenters that 
implementation of AAR requirements on tie lines may necessitate 
increased communication among neighboring transmission providers and 
relevant transmission owners. While we expect that parties will work 
collaboratively to ensure that appropriate ratings are determined for 
each tie line, we decline to adopt specific requirements for 
coordinating AAR implementation across transmission provider seams. 
Parties along these seams have a long history of working 
collaboratively to ensure the reliable implementation of transmission 
facility ratings and we are not persuaded that specific requirements 
for coordination are required at this time. Moreover, we note that, in 
the event of a disagreement over the appropriate facility rating, the 
NERC Reliability Standards already establish a framework for how 
entities should proceed, i.e., that the system should be operated to 
the most limiting parameter.\397\ However, as described further in 
Section IV.G.3.b, to ensure that transmission providers have adequate 
transparency into the transmission line ratings methodologies of their 
neighbors, we require transmission providers to share transmission line 
ratings and transmission line rating methodologies with other 
transmission providers, upon request.
---------------------------------------------------------------------------

    \397\ Reliability Standard TOP-001-5, Requirement R 18, p. 7, 
https://www.nerc.com/pa/Stand/Reliability%20Standards/TOP-001-5.pdf.
---------------------------------------------------------------------------

    173. In response to EEI and NERC, we further clarify that, to the 
extent there is a disagreement among entities about the calculated AAR, 
transmission providers should use the most limiting AAR in order to 
ensure reliability and that thermal limits are respected. As IID 
suggests, however, if the most limiting AAR along a mutual seam is 
based on one transmission provider's ambient air temperature 
assumptions that are more risk averse than another transmission 
provider's ambient air temperature assumptions, the inevitable result 
will be increased congestion between control areas. While using the 
more risk averse transmission line rating may result in an increase in 
congestion relative to the alternative of using a lower forecasted 
ambient air temperature, we do not, in this final rule, revise each 
transmission provider's authority to set the transmission line ratings 
within its control area.
    174. In response to EEI's request for clarification on the 
applicability of the AAR requirements to non-jurisdictional entities, 
we note that the Commission's pro forma OATT requirements apply only to 
Commission-jurisdictional transmission providers. However, to the 
extent non-jurisdictional entities have reciprocity tariffs on file 
with the Commission, such reciprocity tariffs will need to implement 
pro forma OATT Attachment M adopted herein in order to satisfy the 
Commission's comparability (non-discrimination) standards established 
in Order No. 888.
d. Applicability of AARs to Transmission Loading Relief (TLR) Events
i. NOPR Proposal
    175. In the NOPR, the Commission proposed to require transmission 
providers to use AARs as the relevant transmission line rating when 
determining whether to curtail or interrupt point-to-point transmission 
service (under section 14.7 of the pro forma OATT) if such curtailment 
or interruption is necessary because of a reduction in transfer 
capability anticipated to occur (start and end) within the next 10 
days. The Commission also proposed to require transmission providers to 
use AARs as the relevant transmission line rating when determining 
whether to curtail network transmission service or secondary service 
(under section 33 of the pro forma OATT) or redispatch network 
transmission service or secondary service (under sections 30.5 and/or 
33 of the pro forma OATT), if such curtailment or redispatch is both 
necessary because of issues related to flow limits on transmission 
lines and anticipated to occur (start and end) within 10 days of such 
determination.\398\
---------------------------------------------------------------------------

    \398\ NOPR, 173 FERC ] 61,165 at PP 87, 89, 90.
---------------------------------------------------------------------------

ii. Comments
    176. MISO states that the Commission should clarify that use of 
AARs in congestion management should not discriminate based on the type 
of flows being curtailed, be it transmission service or market flow, as 
some processes, such as the interregional TLR process, differentiate 
between the types of flow.\399\
---------------------------------------------------------------------------

    \399\ MISO Comments at 8.
---------------------------------------------------------------------------

iii. Commission Determination
    177. We clarify that AARs should not discriminate based on the type 
of flows being curtailed, interrupted, or redispatched. Accordingly, we 
modify certain aspects of pro forma OATT Attachment M, as proposed in 
the NOPR, to clarify that AARs must be used as the relevant 
transmission line rating when determining whether to initiate TLR 
procedures anticipated to occur (start and end) within the next 10 
days. We note that TLR procedures occur pursuant to the curtailment, 
interruption, and/or redispatch procedures outlined in pro forma OATT 
sections 13.6, 14.7, 30.5, and/or 33, which are also referenced in pro 
forma OATT Attachment M, as proposed in the NOPR, as requiring the use 
of AARs as the relevant transmission line rating.

[[Page 2273]]

In these instances, we find that proposed pro forma OATT Attachment M 
is already sufficiently clear: AARs must be used as the relevant 
transmission line rating when determining whether to initiate TLR 
procedures anticipated to occur (start and end) within the next 10 
days. However, because pro forma OATT Attachment M, as proposed in the 
NOPR, only referenced curtailment and interruption procedures that 
occur pursuant to pro forma OATT section 14.7, for clarity, we modify 
the proposed pro forma OATT Attachment M to also reference curtailment 
and interruption procedures that occur pursuant to pro forma OATT 
section 13.6.
e. Communication and Verification of AARs
i. Comments
    178. With regard to the Commission's NOPR proposal that AAR data be 
submitted by the transmission owner to the RTO/ISO through Supervisory 
Control and Data Acquisition (SCADA) or related systems, MISO states 
that it strongly urges the Commission not to require any specific data 
communication medium due to rapid and frequent changes in technology. 
MISO emphasizes that the scale and scope of AARs as proposed in the 
NOPR would require electronic and programmatic updates to the RTO/ISO, 
and using manual communication methods, such as phone calls or written 
messaging, would not be practical. MISO adds that the requirements to 
coordinate data interchange for reliability are currently regulated by 
the NERC Reliability Standards.\400\ CAISO states that a fundamental 
challenge will be to ensure entities can transmit forecasted AARs in a 
timely manner.\401\ As a result of this challenge, CAISO requests 
clarification on what to do in cases of communication failure between 
the transmission owner and the RTO's/ISO's EMS and what an RTO/ISO 
should do if a transmission owner submits an incorrect transmission 
line rating.\402\ NYISO clarifies that it receives updates of 
transmission line ratings from asset owners via the Inter-Control 
Center Communication Protocol.\403\ NYTOs explain that, since AARs and 
DLRs are constantly changing, independent software validation solutions 
will be needed to avoid violating NERC Reliability Standard FAC-008, 
which would occur when there is any accidental discrepancy between a 
calculated transmission line rating and the transmission line rating 
methodology.\404\
---------------------------------------------------------------------------

    \400\ MISO Comments at 15-16.
    \401\ CAISO Comments at 4-5.
    \402\ Id. at 12-13.
    \403\ NYISO Comments at 4.
    \404\ NYTOs Comments at 7.
---------------------------------------------------------------------------

ii. Commission Determination
    179. In response to comments requesting that the Commission not 
dictate communication mediums for transmission owners submitting AARs 
to RTOs/ISOs, we clarify that this final rule requires that electronic 
transmission line rating data be submitted by transmission owners 
directly into an RTO's/ISO's EMS through SCADA or similar communication 
systems. We clarify that other electronic systems, such as Inter-
Control Center Communication Protocol, can be used to comply with this 
requirement, and RTOs/ISOs may propose to use such systems on 
compliance.
    180. In response to concerns about potential scarcity of 
temperature data and/or AAR communication failures, we modify the NOPR 
proposal to require that, if an AAR otherwise required to be used under 
pro forma OATT Attachment M is unavailable, the transmission provider 
must use the relevant seasonal line rating as the appropriate 
transmission line rating. This requirement does not relieve any 
transmission provider of the obligation in the first instance to 
provide an AAR but provides an alternate only if an AAR otherwise 
required under pro forma OATT Attachment M is not available. Further, 
while this provision establishes the seasonal line rating as the 
default recourse rating, the transmission provider retains the ability 
under the ``System Reliability'' section of pro forma OATT Attachment M 
to use a different recourse rating where the transmission provider 
reasonably determines such a rating is necessary to ensure the safety 
and reliability of the transmission system.
    181. In response to NYTOs' comments that changing transmission line 
ratings will necessitate additional transmission line rating validation 
tools, we reiterate that the definitions of Transmission Line Rating, 
AARs, and Seasonal Line Rating we adopt in this final rule--as set 
forth in pro forma OATT Attachment M--require computation of 
transmission line ratings in accordance with good utility practice, 
including up-to-date forecasts, to ensure the accuracy of the relevant 
transmission line rating.\405\ And as NYTOs note, inaccurate 
transmission line ratings or a discrepancy between transmission line 
ratings and the transmission line rating methodology could trigger a 
violation of NERC Reliability Standard FAC-008 by the relevant 
transmission owner. In other words, pro forma OATT Attachment M imposes 
an affirmative obligation on transmission providers to implement 
accurate transmission line ratings and the NERC Reliability Standards 
similarly require accuracy in transmission line ratings by the 
transmission owners that calculate such ratings. In RTOs/ISOs, where 
the transmission provider (i.e., the RTO/ISO) must rely on its 
transmission owners to calculate and provide the required transmission 
line ratings, we acknowledge that there might be some increased 
complexity in ensuring the accuracy of the transmission line ratings. 
However, we do not prescribe the method for a transmission provider--
including an RTO/ISO--to screen for issues with transmission line 
ratings,\406\ instead leaving it up to the transmission provider to 
develop a general validation system that ensures its compliance with 
the requirements of this final rule and relevant NERC Reliability 
Standards. We agree with MISO that it is unable--and indeed is not 
required--to audit transmission line ratings; \407\ rather, the type of 
validation that we reference here would be akin to the automated 
validation referenced by CAISO, SPP, and PJM,\408\ where the RTO/ISO 
runs checks for obvious signs of data errors or corruption.
---------------------------------------------------------------------------

    \405\ Pro Forma OATT attach. M, AAR Definition.
    \406\ For example, a transmission provider might consider 
screening for such issues as: Missing data; significant changes in 
transmission line ratings; illogical data (such as ratings that 
increase with increasing temperature, or daytime ratings that are 
higher than nighttime ratings); and transmission line ratings 
outside feasible ranges for particular transmission lines.
    \407\ MISO Comments at 27.
    \408\ PJM Comments at 8; CAISO Comments at 13; SPP Comments at 
5-6. We note that, according to the MISO Transmission Owners' 
Agreement (TOA), MISO also has a responsibility to verify 
transmission line ratings. MISO, Open Access Transmission, Energy 
and Operating Reserve Markets Tariff, Rate Schedule 1, Appendix B, 
Section V (30.0.0) (``Each Owner shall file with MISO information 
regarding the physical ratings of all of its equipment in the 
Transmission System. This information is intended to reflect the 
normal and emergency ratings routinely used in regional load flow 
and stability analyses. In carrying out its responsibilities, MISO 
shall apply ratings that have been provided by the respective Owners 
and have been verified and accepted as appropriate by MISO where 
such ratings affect MISO reliability.'').
---------------------------------------------------------------------------

    182. In response to CAISO's request for clarification on what an 
RTO/ISO should do if a transmission owner submits an incorrect 
transmission line rating, we do not require RTOs/ISOs to audit or 
recalculate transmission line ratings submitted to them (except in 
instances where their procedures provide for them to calculate

[[Page 2274]]

transmission line ratings, such as for RTOs/ISOs that calculate AARs 
from tables or databases). To the extent any transmission provider 
becomes aware of an apparent inaccurate transmission line rating, the 
transmission provider is expected to inform the transmission owner 
immediately and both the transmission provider and transmission owner 
should take appropriate action to correct any inaccuracy. If the 
transmission provider and transmission owner are unable to resolve the 
inaccuracy of a submitted AAR, then, as discussed above, the 
transmission provider must use an appropriate recourse rating until the 
AAR inaccuracy is resolved. To the extent the transmission provider 
and/or transmission owner is out of compliance with any applicable 
requirements, they should report such noncompliance as dictated by the 
applicable requirement.
f. Minimum AAR Temperature Range and AAR Granularity
i. Comments
    183. Vistra contends that the Commission should provide guidance on 
the range and granularity of temperatures to be used in AARs.\409\ 
Vistra argues that the Commission's AAR policy will be undermined if 
implementation decisions reintroduce unnecessary conservativism (such 
as only altering AARs for every 20 degrees Fahrenheit of ambient air 
temperature, or developing AARs for only a limited range of ambient air 
temperatures).\410\ Vistra suggests that it would not be unreasonable 
for AARs to change for every one or two degrees Fahrenheit change in 
ambient air temperature, and that AARs be calculated for a range of 
temperatures that cover the historical low and historical high 
temperature plus some margin (e.g., 10 degrees).\411\ Vistra argues 
that recent extreme temperature events illustrate that temperatures can 
exceed historical levels with important reliability implications.\412\
---------------------------------------------------------------------------

    \409\ Vistra Comments at 6-7.
    \410\ Id. at 6.
    \411\ Id. at 6-7.
    \412\ Id. at 7.
---------------------------------------------------------------------------

    184. ITC asserts that the Commission should adopt a transmission 
line rating ``floor'' where no AAR would fall below the lowest seasonal 
line rating and states that operational risk and planning issues 
outweigh any benefit of exceeding such a floor given how rarely ambient 
air temperatures exceed those associated with the lowest seasonal line 
rating.\413\
---------------------------------------------------------------------------

    \413\ ITC Comments at 15-16.
---------------------------------------------------------------------------

ii. Commission Determination
    185. In response to Vistra's comments, we clarify that any methods 
for determining AARs must be valid for at least the range of local 
historical temperatures (over the entire period for which records are 
available) plus or minus a margin of 10 degrees Fahrenheit, in order to 
meet the pro forma OATT Attachment M requirement that an AAR reflect an 
up-to-date forecast of ambient air temperature. For example, if the 
historical range is -30 degrees Fahrenheit to 107 degrees Fahrenheit, 
the valid range must be at least -40 degrees Fahrenheit to 117 degrees 
Fahrenheit. Where a transmission provider uses pre-calculated AARs 
within a look-up table or similar database, such values must be 
calculated for all temperatures within such a valid range. Similarly, 
where a transmission provider uses a formula or computer program to 
calculate AARs based on forecasted temperatures, such a formula/program 
must be accurate across such a valid range. Furthermore, transmission 
providers must have procedures in place to handle a situation where 
forecast temperatures fall outside of such a range of temperatures, to 
ensure that safe and reliable transmission line ratings are used. 
Finally, in the event that actual temperatures set new high or low 
records, transmission providers are required to revise their look-up 
tables/databases or formulas/programs, as necessary and within a timely 
manner, to maintain the 10 degree Fahrenheit margin.
    186. We agree with Vistra's assertion that recent extreme 
temperature events in California and Texas illustrate that temperatures 
can exceed historical levels with significant economic and reliability 
implications.\414\ The clarification that any methods for determining 
AARs must be valid for at least the range of local historical 
temperatures plus or minus a margin of 10 degrees Fahrenheit ensures 
that, when such severe and unexpected weather events do occur, 
transmission providers will be prepared and able to continue to 
implement more accurate transmission line ratings.
---------------------------------------------------------------------------

    \414\ Vistra Comments at 6-7.
---------------------------------------------------------------------------

    187. With respect to the requirement for AARs to reflects an up-to-
date forecast of ambient air temperatures, as Vistra points out, absent 
clarification, some implementations of AARs may not result in an AAR 
change with every change in forecasted temperature (e.g., 
implementations that use pre-calculated look-up tables or databases, 
where AARs do not change within each temperature ``step''). For this 
reason, we clarify that a transmission provider must implement AARs 
that update at least with every five degree Fahrenheit increment of 
temperature change, in order to meet the pro forma OATT Attachment M 
requirement that an AAR reflect an up-to-date forecast of ambient air 
temperature. For example, an AAR is not consistent with the 
requirements of pro forma OATT Attachment M if it results in 
transmission line ratings that do not change when temperature forecasts 
increase or decrease by five degrees Fahrenheit. This clarification is 
consistent with ERCOT's AAR implementation, which utilizes AAR look-up 
tables that define AARs in five-degree Fahrenheit steps.\415\ We find 
that larger steps may introduce inaccuracies into transmission line 
ratings, resulting in wholesale rates that are unjust and unreasonable. 
Moreover, as Vistra suggests, a minimum amount of AAR temperature 
granularity is necessary to ensure that transmission line ratings 
sufficiently reflect changes in ambient air temperatures.\416\
---------------------------------------------------------------------------

    \415\ Commission Staff Paper at 7.
    \416\ Vistra Comments at 6-7.
---------------------------------------------------------------------------

    188. We decline to require a transmission line rating ``floor'' 
whereby no AAR would fall below the lowest seasonal line rating, as 
requested by ITC. Seasonal line ratings are generally already 
calculated to reflect worst-case weather conditions. However, to the 
extent that a transmission provider experiences extreme temperatures 
that exceed seasonal assumptions, the resulting transmission line 
ratings will be more accurate than seasonal line ratings and will send 
important price signals to market participants. In such circumstances, 
transmission providers should be able to plan for such extreme 
temperatures given current temperature forecasting capabilities.
g. AAR Liabilities
i. Comments
    189. Transmission owners also discuss and request protection from 
liabilities, which might result from AAR implementation. For example, 
explaining that using AARs in the day-ahead and/or real-time market may 
result in different congestion patterns than were anticipated, MISO 
Transmission Owners argue that transmission owners should not be 
responsible for any resulting uplift or for any impacts on the value of 
financial transmission rights (FTR) or the value of other market 
trades, uplift costs, or other losses resulting from the

[[Page 2275]]

implementation of AARs. MISO Transmission Owners also contend that the 
Commission should absolve transmission owners from tariff violations 
resulting from last minute transmission line rating changes to protect 
public safety.\417\
---------------------------------------------------------------------------

    \417\ MISO Transmission Owners Comments at 18-21.
---------------------------------------------------------------------------

    190. Some commenters discuss the implications of the proposed pro 
forma OATT Attachment M for the FTR markets.\418\ MISO and EEI also 
urge liability protections, explaining that absent liability 
protections, RTOs/ISOs and their members could be subject to liability 
if the weather is predicted incorrectly. MISO and EEI explain that 
implementing AARs in the day-ahead market could result in differences 
between the transmission line ratings used in FTR markets, and thereby 
impact the value of congestion rights. MISO and EEI further explain 
that if weather shifts unexpectedly, reliance on AARs could result in 
too much or too little being committed in the day-ahead market, causing 
financial impacts. MISO and EEI state that potential liability could 
also arise from possible reliability events for which it is 
subsequently determined that a more conservative transmission line 
rating could have prevented.\419\ Explaining that in CAISO's congestion 
revenue rights (CRR) market ratepayers can be exposed to substantial 
losses after they become the CRR counterparty in the event some CRR 
auction capacity is left unpurchased, the CAISO DMM argues that 
transmission line ratings used in CRR auction models should still be 
the most conservative limits for those transmission lines instead of 
any higher limit enabled through hourly transmission line ratings.\420\ 
The SPP MMU suggests that the implementation of AARs and DLRs should be 
coincident with an annual transmission congestion rights (TCR) auction, 
or the status of implementation should be clearly communicated to 
auction participants.\421\
---------------------------------------------------------------------------

    \418\ MISO Comments at 21; EEI Comments at 12; CAISO DMM 
Comments at 3-4, 8-9; SPP MMU Comments at 11.
    \419\ MISO Comments at 21; EEI Comments at 12.
    \420\ CAISO DMM Comments at 3-4, 8-9.
    \421\ SPP MMU Comments at 11.
---------------------------------------------------------------------------

    191. ITC also asks that the Commission clarify that transmission 
owners will not be liable for any market inefficiencies that arise from 
inaccurate transmission line ratings, provided the transmission line 
ratings are communicated to the transmission provider in good 
faith.\422\
---------------------------------------------------------------------------

    \422\ ITC Comments at 3.
---------------------------------------------------------------------------

ii. Commission Determination
    192. We decline to provide explicit liability protections related 
to AAR implementation, as requested by commenters. We are not persuaded 
that this final rule's AAR reforms introduce additional liabilities 
that do not already exist. To the extent there are liability concerns 
associated with transmission line ratings changing in real time, these 
concerns already exist today as RTOs/ISOs forecast load and asset 
owners forecast renewable energy availability in real time. Moreover, 
FTR auctions, like all forward planning activities, already make a 
variety of forward assumptions about transmission availability that do 
not necessarily materialize in real-time operations. As the Commission 
stated in the NOPR, RTOs/ISOs already periodically request, and 
transmission owners periodically provide, ad hoc transmission line 
rating changes based on differences between actual and assumed ambient 
air temperatures.\423\ In those cases, as long as utilities operate in 
a manner consistent with good utility practice, blanket liability 
protection is not necessary. Nevertheless, we note that transmission 
providers could submit filings pursuant to FPA section 205 to the 
Commission to propose revised liability protections in their tariffs to 
the extent they believe such protections are warranted.
---------------------------------------------------------------------------

    \423\ NOPR, 173 FERC ] 61,165 at P 107.
---------------------------------------------------------------------------

C. Seasonal Line Ratings

1. Seasonal Line Ratings Requirements
a. NOPR Proposal
    193. In the NOPR, the Commission proposed to require transmission 
providers to use seasonal line ratings when evaluating requests for 
other (longer-term) point-to-point transmission service, i.e., requests 
for point-to-point transmission service ending more than 10 days from 
the date of the request. Specifically, the Commission proposed to 
require transmission providers to use seasonal line ratings as the 
relevant transmission line ratings when: (1) Evaluating requests for 
longer-term point-to-point transmission service; (2) responding to 
requests for information on the availability of such longer-term point-
to-point transmission service (including requests for ATC or other 
information related to such potential service); and (3) posting ATC or 
other information related to such longer-term point-to-point 
transmission service to their OASIS site.
    194. For network transmission service, the Commission proposed to 
require transmission providers to evaluate requests to designate 
network resources (under section 30 of the pro forma OATT) or network 
load (under section 31 of the pro forma OATT) based on seasonal line 
ratings because the Commission found that such designations are 
generally long-term requests and seasonal line ratings better reflect 
conditions over a longer term than AARs.
    195. The Commission further proposed to require transmission 
providers to use seasonal line ratings as the relevant transmission 
line ratings when determining whether to curtail or interrupt point-to-
point transmission service (under section 14.7 of the pro forma OATT) 
in situations other than those in which such curtailment or 
interruption is necessary because of a reduction in transfer capability 
anticipated to occur (start and end) within the next 10 days. The 
Commission similarly proposed to require transmission providers to use 
seasonal line ratings as the relevant transmission line rating for 
determining the necessity of curtailment or redispatch of network 
transmission service or secondary service in situations other than 
those in which such curtailment or redispatch is necessary because of a 
reduction in transfer capability anticipated to occur within the next 
10 days.\424\
---------------------------------------------------------------------------

    \424\ Id. PP 88, 90.
---------------------------------------------------------------------------

b. Comments
    196. Some commenters support \425\ and others generally do not 
oppose the Commission's NOPR proposal to require transmission providers 
to use seasonal line ratings for transmission service requests and for 
curtailments, interruptions, and redispatch beyond the 10-day 
threshold. Some commenters argue that the Commission should go further 
by requiring that seasonal line ratings be used in transmission 
planning \426\ and/or that more granular alternatives be used when 
examining transmission service involving wind resources.\427\ CAISO and 
ISO-NE note that summer and winter seasonal line ratings are already 
used by transmission owners in their respective regions.\428\ On the 
other hand, MISO Transmission Owners contend that the Commission should 
require seasonal line ratings in long-term transmission operations and 
planning only when it is beneficial to do

[[Page 2276]]

so.\429\ Similarly, Entergy argues that the Commission should not 
mandate the use of seasonal line ratings, explaining that it does not 
use seasonal line ratings, and that, instead, it uses AARs on a one-
day, two-day, or hourly basis because AARs are more accurate. Entergy 
claims that maximum monthly temperatures in its service territory do 
not differ significantly enough for seasonal line ratings to create any 
value and therefore requirements to calculate seasonal line ratings 
would result in increased costs without commensurate benefits.\430\
---------------------------------------------------------------------------

    \425\ See, e.g., AEP Comments at 1; EDFR Comments at 7.
    \426\ ACPA/SEIA Comments at 15-16.
    \427\ Clean Energy Parties Comments at 12.
    \428\ CAISO Comments at 3, ISO-NE Comments at 6.
    \429\ MISO Transmission Owners Comments at 17-18.
    \430\ Entergy Comments at 15.
---------------------------------------------------------------------------

    197. SPP requests clarification on whether the seasonal line rating 
requirements are intended to apply to transmission service requests 
longer than one year in duration.\431\
---------------------------------------------------------------------------

    \431\ SPP Comments at 7.
---------------------------------------------------------------------------

c. Commission Determination
    198. We adopt the Commission's proposal in the NOPR to require 
transmission providers to use seasonal line ratings as the appropriate 
transmission line ratings when: (1) Evaluating requests for 
transmission service--including point-to-point, network, and secondary 
service--ending more than 10 days from the date of the request; (2) 
responding to requests for information on the availability of such 
transmission service (including requests for ATC or other information 
related to potential transmission service); and (3) posting 
transmission availability (including ATC for point-to-point 
transmission service requests) or other information related to 
transmission service to their OASIS site.
    199. Additionally, we adopt the Commission's proposal in the NOPR 
to require transmission providers to use seasonal line ratings as the 
relevant transmission line ratings when determining whether to curtail 
or interrupt non-firm point-to-point transmission service (under 
section 14.7 of the pro forma OATT) in situations other than those in 
which such curtailment or interruption is necessary because of issues 
related to flow limits on transmission lines anticipated to occur 
(start and end) within the next 10 days. We also require transmission 
providers to use seasonal line ratings when determining whether to 
curtail or interrupt firm point-to-point transmission service under 
section 13.6 of the pro forma OATT in such situations.
    200. We also adopt the NOPR proposal to require seasonal line 
ratings be used as the relevant transmission line rating for 
determining the necessity of curtailment (under section 33 of the pro 
forma OATT) or redispatch (under sections 30.5 and/or 33 of the pro 
forma OATT) of network or secondary service in situations other than 
those in which such curtailment or redispatch is necessary because of 
issues related to flow limits on transmission lines anticipated to 
occur within the next 10 days. We continue to find that seasonal line 
ratings are the appropriate transmission line rating for evaluations of 
longer-term transmission service requests because ambient air 
temperature forecasts for such future periods have more uncertainty 
than near-term forecasts, and thus tend to converge to the longer-term 
ambient air temperature forecasts used in seasonal line ratings. The 
requirements for seasonal line ratings we adopt in this section are set 
forth under ``Obligations of Transmission Provider'' in pro forma OATT 
Attachment M.
    201. In response to arguments from MISO Transmission Owners and 
Entergy that the Commission should not require seasonal line ratings or 
should do so only on a limited basis, we find that seasonal line 
ratings are needed to ensure that transmission line ratings used for 
evaluating requests for longer-term transmission service are accurate 
and result in just and reasonable wholesale rates. In response to 
Entergy's comment regarding its use of AARs instead of seasonal line 
ratings because AARs are more accurate, the seasonal line ratings 
requirements adopted herein do not prevent Entergy from using AARs for 
near-term transmission service, and in fact we require AARs to be used 
for near-term transmission service. Seasonal line ratings are only 
required to be used for longer-term transmission service. Entergy also 
claims that its maximum temperatures do not vary sufficiently across 
the year for seasonal line ratings to provide value. We find that, in 
general, temperatures vary sufficiently across seasons of the year for 
seasonal line ratings to provide value. We also find that the burden of 
implementing seasonal line ratings is particularly low.
    202. In response to SPP's comments, we clarify that the 
requirements for seasonal line rating implementation do apply to 
transmission service requests longer than one year in duration. To the 
extent SPP's comments reflect any confusion about how to apply seasonal 
line ratings to service longer than a season, we clarify that such 
requests should be approved or denied (or availability should be 
determined) based on whether the requested service can be accommodated 
in each season (given the applicable seasonal line ratings).
    203. We decline to adopt ACPA/SEIA's suggestion that seasonal line 
ratings should be required for transmission planning. Such a 
requirement is beyond the scope of this rulemaking, which is focused on 
remedying unjust and unreasonable wholesale rates resulting from 
inaccurate transmission line rating assumptions used in requests for 
transmission service and in transmission operations. We note that the 
Commission recently initiated a proceeding to examine a broad range of 
transmission-related issues, including regional transmission planning, 
in its July 2021 Advance Notice of Proposed Rulemaking in Docket No. 
RM21-17-000.\432\
---------------------------------------------------------------------------

    \432\ Building for the Future Through Electric Regional 
Transmission Planning and Cost Allocation and Generator 
Interconnection, 86 FR 40266 (July 27, 2021), 176 FERC ] 61,024 
(2021).
---------------------------------------------------------------------------

2. Seasonal Line Rating Implementation Requirements
a. NOPR Proposal
    204. In the NOPR, the Commission proposed to define a seasonal line 
rating in pro forma OATT Attachment M as ``a transmission line rating 
that: (a) Applies to a specified season, where seasons are defined by 
the transmission provider to not include more than three months in each 
season; (b) reflects an up-to-date forecast of ambient air temperature 
across the relevant season over which the rating applies; and (c) is 
calculated monthly, if not more frequently, for each season in the 
future for which transmission service can be requested.'' \433\
---------------------------------------------------------------------------

    \433\ Proposed pro forma OATT attach. M, Seasonal Line Rating 
definition.
---------------------------------------------------------------------------

b. Comments
    205. Many entities comment on the Commission's NOPR proposal to 
define ``seasonal line rating'' as a season which includes no more than 
three months. These entities predominately request flexibility for 
transmission providers to define seasonal line ratings in a manner 
appropriate to their climate.\434\ For example, NRECA/LPPC contend that 
seasons do not fall into neat three-month windows and that shoulder 
months on either side of the summer season may resemble summer 
conditions more than fall or spring. For this reason, NRECA/LPPC 
recommend that the definition of seasonal line

[[Page 2277]]

ratings be revised to accommodate regional considerations.\435\ MISO 
Transmission Owners argue that the Commission should not require 
seasonal line rating durations to be limited to no more than three 
months because weather patterns vary widely.\436\
---------------------------------------------------------------------------

    \434\ NRECA/LPPC Comments at 23-24; MISO Transmission Owners 
Comments at 18; Entergy Comments at 15; SPP Comments at 8; EEI 
Comments at 9; ITC Comments at 9-10; MISO Comments at 20-21; SDG&E 
Comments at 3.
    \435\ NRECA/LPPC Comments at 23-24.
    \436\ MISO Transmission Owners Comments at 18.
---------------------------------------------------------------------------

    206. Duke Energy similarly states that temperatures in its Florida 
service territory do not differ enough to justify seasonal line 
ratings. Duke Energy also argues that, at a minimum, the Commission 
should clarify that one seasonal line rating set may have transmission 
line ratings equal to another seasonal line rating set, as long as the 
transmission line ratings are consistent with historically observed 
and/or expected weather patterns.\437\ MISO states that requiring 
seasonal line ratings to be unique from season to season may introduce 
arbitrary differences in seasonal line ratings.\438\
---------------------------------------------------------------------------

    \437\ Duke Energy Comments at 12.
    \438\ MISO Comments at 20-21.
---------------------------------------------------------------------------

    207. ITC also asserts that the Commission should allow transmission 
owners to determine the number and length of seasons in their service 
territory so that seasonal line rating definitions may recognize 
differences in regional climates.\439\ PacifiCorp states that it 
currently only uses summer and winter ratings and that implementation 
of the proposed three month seasonal requirements would require 
substantial expansion to its Weak Link databases.\440\ PacifiCorp 
further states that firm contractual commitments may need to be 
reexamined and remedied if previously granted levels of transmission 
service cannot be honored under this seasonal line ratings 
construct.\441\
---------------------------------------------------------------------------

    \439\ ITC Comments at 9-10.
    \440\ PacifiCorp Comments at 3.
    \441\ Id. at 7.
---------------------------------------------------------------------------

    208. SPP notes that the three-month season duration conflicts with 
the four-month season length established by SPP's stakeholders.\442\
---------------------------------------------------------------------------

    \442\ SPP Comments at 8.
---------------------------------------------------------------------------

    209. Other commenters question the proposed requirement for a 
``seasonal line rating'' to ``forecast'' ambient air temperatures 
across the relevant season. SDG&E, for example, questions the value of 
basing seasonal line ratings for future seasons on weather forecast 
data, stating that such data is statistically insignificant that far 
into the future and instead suggests basing seasonal line ratings on 
historical weather data, specifically a 12-month, static data set per 
calendar month.\443\ MISO Transmission Owners also state that the NOPR 
proposal would require seasonal line ratings to be based on forecasts, 
not historical data, as is currently used to develop seasonal line 
ratings.\444\ MISO strongly urges the Commission to allow seasonal line 
ratings to be established based on historical data rather than 
forecasts because historical temperature data is known and thus more 
reliable than predictions. MISO contends that using forecast data would 
risk greater certainty.\445\
---------------------------------------------------------------------------

    \443\ SDG&E Comments at 3.
    \444\ MISO Transmission Owners Comments at 34.
    \445\ MISO Comments at 21.
---------------------------------------------------------------------------

    210. Finally, some commenters protest the proposed requirement for 
seasonal line ratings to be ``calculated monthly, if not more 
frequently, for each season in the future for which transmission 
service can be requested.'' Multiple commenters argue that this monthly 
updating requirement provides little value or can cause additional 
problems.\446\ ITC argues that monthly updates to seasonal line ratings 
could cause significant uncertainty in planning processes and requests 
that the Commission instead only require seasonal line ratings be 
calculated for the duration of a single season.\447\ Exelon explains 
that it does not update seasonal line ratings monthly, that its 
seasonal line ratings use historical temperatures to make assumptions 
on future maximum temperatures, and that those assumptions typically do 
not change. Exelon contends that there would not be any value in 
regularly reassessing seasonal line rating assumptions and instead 
suggests the following revision to the proposed definition of seasonal 
line rating: ``reflects a forecast of ambient air temperatures across 
the relevant season over which the rating applies.'' \448\ MISO, on the 
other hand, contends that seasonal line ratings, once established, 
should be reviewed when equipment changes are made, climate or weather 
data necessitates, or when otherwise prudent.\449\
---------------------------------------------------------------------------

    \446\ Exelon Comments at 12-13; EEI Comments at 8-9; ITC 
Comments at 11; SDG&E Comments at 3.
    \447\ ITC Comments at 11.
    \448\ Exelon Comments at 12-13.
    \449\ MISO Comments at 21.
---------------------------------------------------------------------------

c. Commission Determination
    211. In response to comments requesting that the Commission provide 
flexibility for seasonal line ratings to cover periods greater than 
three months, we modify the Commission's proposed requirement in the 
NOPR for how transmission providers define seasons, to provide 
additional flexibility. Specifically, rather than prohibiting 
transmission providers from including more than three months in each 
season, we instead require that transmission providers define seasons 
to include not fewer than four seasons in each year, and to reasonably 
reflect portions of the year where expected high temperatures are 
relatively consistent. Seasonal line ratings typically encompass six 
months. Six-month seasonal line ratings, however, necessarily require a 
worst-case weather representation specific to a specific month to be 
applied to every other month. In that context, ``summer'' seasonal line 
ratings could be, and often are, applied to the months of May through 
October despite the average historic high temperature in October, in 
much of the country, being considerably different than July's average 
historic high temperature. Moreover, ``winter'' seasonal line ratings 
could be, and often are, applied to the months of November through 
April despite the average historic high temperature in April, in much 
of the country, being considerably different than January's average 
historic high temperature. As with AARs, using unrealistic temperature 
assumptions will result in inaccurate seasonal line ratings, and, in 
turn, unjust and unreasonable wholesale rates.
    212. However, we clarify that a transmission provider may define 
seasons shorter than three months, and/or have more than four seasons 
for its seasonal line rating program. For example, if a transmission 
provider found through its analysis that its system had a five-month 
``summer'' period that was characterized by a consistent high 
temperature, that transmission provider could accommodate such a period 
by defining a three-month Summer 1 season, and a two-month Summer 2 
season, and independently determining the seasonal line ratings (based 
on an independent analysis of temperatures) for each season. We further 
clarify, in response to comments from MISO, Entergy, and Duke Energy, 
that seasonal line ratings are not required to be arbitrarily different 
between seasons. As long as such ratings are uniquely determined in 
accordance with the relevant requirements, it is not prohibited for 
seasonal line ratings to be the same across different seasons if the 
independent analyses support those ratings, although we expect such 
instances will be infrequent.
    213. In response to comments from PacifiCorp about the cost 
associated with implementing seasonal line ratings with three-month 
granularity, we appreciate that this three-month granularity 
requirement represents some level of burden, but we believe that the 
burden in most cases will be relatively low. Moreover, in cases such as

[[Page 2278]]

PacifiCorp describes, we believe that seasonal line ratings with a 
three-month granularity represent a more accurate representation of 
existing transfer capabilities and that using a more accurate 
representation of existing transfer capabilities will require 
transmission providers to more accurately examine the feasibility of 
existing contracts.
    214. In doing so, our expectation is that, in at least certain 
circumstances, transmission providers will find that certain existing 
approved transmission service, accepted based on six-month winter 
seasonal air temperature assumptions of 32 degrees Fahrenheit (or other 
similar assumptions), are not able to be effectuated without 
curtailment, interruption, and/or redispatch, given likely warmer 
temperatures in shoulder periods falling within that six-month winter 
season.
    215. In response to comments discussing the burden of calculating 
seasonal line ratings monthly, we modify the definition of seasonal 
line rating proposed in the NOPR to require that seasonal line ratings 
be calculated ``annually, if not more frequently,'' rather than 
``monthly, if not more frequently.'' We adopt the remainder of the 
definition unchanged from the Commission's proposal in the NOPR. We 
agree with MISO that seasonal line ratings, once established, should be 
reviewed when equipment changes are made, climate or weather data 
necessitates, or when otherwise prudent. However, we also agree with 
commenters concerned about the burden of calculating monthly updates to 
seasonal line ratings and are persuaded that the underlying weather 
assumptions of seasonal line ratings are unlikely to change on a 
monthly basis. We believe that a requirement for annual recalculations 
of seasonal line ratings strikes an appropriate balance between 
ensuring seasonal line ratings continue to be accurate as weather 
patterns change,\450\ and the costs associated with updating such 
transmission line ratings on a regular basis.
---------------------------------------------------------------------------

    \450\ ACPA/SEIA Comments at 8, 11; EPSA Comments at 4; New 
England State Agencies Comments at 6.
---------------------------------------------------------------------------

    216. Finally, in response to comments that seasonal line ratings 
should be allowed to be based on historical temperatures, rather than 
forecasted temperature values, we clarify that seasonal line ratings 
may be derived from historical temperatures. Seasonal line ratings are 
an important input to longer-term sales for transmission service, and 
in that context are inherently forward-looking, but, given the 
challenges of forecasting future temperatures discussed in Section 
IV.b.2.a, seasonal line ratings may be based on historical 
temperatures, as long as such practices are consistent with good 
utility practice and otherwise meet the requirements in pro forma OATT 
Attachment M.

D. Exceptions and Alternate Ratings

1. NOPR Proposal
    217. In the NOPR, the Commission proposed to require the use of 
AARs in many instances but allowed for the use of an alternative 
transmission line rating when a transmission provider determines that a 
transmission line is not affected by ambient air temperatures. 
Specifically, the Commission stated that not all transmission line 
ratings are affected by ambient air temperatures, either because the 
technical transfer capability of the limiting conductors and/or 
limiting transmission equipment is not dependent on ambient air 
temperatures, or because the transmission line's transfer capability is 
limited not by ambient air temperatures but by a transmission system 
limit such as a system voltage or stability limit. For this reason, the 
proposed language under the ``Exceptions'' paragraph of pro forma OATT 
Attachment M accommodates such transmission lines without requiring 
unwarranted calculations or updates. Attachment M provides that, 
consistent with good utility practice, where the transmission provider 
determines that a transmission line is not affected by ambient air 
temperatures, the transmission provider may use a transmission line 
rating for that transmission line that is not an AAR or seasonal line 
rating.\451\
---------------------------------------------------------------------------

    \451\ NOPR, 173 FERC ] 61,165 at P 103.
---------------------------------------------------------------------------

    218. Additionally, the Commission proposed in the NOPR to include, 
in pro forma OATT Attachment M under the ``System Reliability'' 
section, a reliability ``safety valve.'' This exception provides that, 
if the transmission provider reasonably determines, consistent with 
good utility practice, that the temporary use of a transmission line 
rating different than would otherwise be required by pro forma OATT 
Attachment M is necessary to ensure the safety and reliability of the 
transmission system, then the transmission provider will use such an 
alternate transmission line rating.\452\
---------------------------------------------------------------------------

    \452\ Proposed pro forma OATT attach. M, ``System Reliability''.
---------------------------------------------------------------------------

2. Comments
    219. Several commenters state that certain transmission elements, 
such as underground cables, are not exposed to ambient air 
temperatures, and thus should be exempt from the AAR requirements.\453\ 
For example, NYISO explains that many of its thermally limited 
transmission elements are underground cables.\454\ While NYTOs note 
that NYPA and Consolidated Edison have piloted the use of DLRs on 
underground cables,\455\ NYISO and NYTOs explain that underground cable 
ratings are typically the result of line-specific operating conditions 
(e.g., thermal issues in the oil-filled pipe) and generally do not vary 
with ambient air temperatures.\456\ For this reason, NYISO and NYTOs do 
not support AAR implementation on underground cables.\457\ PJM and 
Eversource similarly request an exception from the proposed AAR 
requirements for underground cables, noting that their ratings are not 
affected by ambient air temperatures.\458\
---------------------------------------------------------------------------

    \453\ See, e.g., NYISO Comments at 8-9; NYTOs Comments at 8; PJM 
Comments at 6; LADWP Comments at 8.
    \454\ NYISO Comments at 8.
    \455\ NYTOs Comments at 4.
    \456\ NYISO Comments at 4; NYTOs Comments at 8.
    \457\ NYISO Comments at 8-9; NYTOs Comments at 8.
    \458\ PJM Comments at 6; Eversource Comments at 3.
---------------------------------------------------------------------------

    220. NYTOs and NRECA/LPPC contend that AARs may not be appropriate 
on older transmission facilities.\459\ For example, NRECA/LPPC assert 
that a transmission provider should be allowed to obtain a waiver from 
the AAR requirements when implementation would be too difficult or 
costly, noting that this may especially be the case for older 
transmission facilities.\460\ Relatedly, EEI includes asset health as 
one consideration that might be taken into account by transmission 
owners in their recommendation for transmission owners to study AAR 
implementation and propose candidate AAR transmission lines.\461\
---------------------------------------------------------------------------

    \459\ NYTOs Comments at 7; NRECA/LPPC Comments at 22.
    \460\ NRECA/LPPC Comments at 22.
    \461\ EEI Comments at 7.
---------------------------------------------------------------------------

    221. NRECA/LPPC contend that the AAR requirements should not apply 
to transmission lines that are not part of the bulk electric system 
operated above 100 kV.\462\ Entergy similarly contends that AARs should 
not be required on facilities operated at or below 69 kV stating that 
such facilities are more likely to include underbuilds, such as

[[Page 2279]]

third-party telecommunications facilities, and that, as a result, the 
use of AARs on such facilities could have significant third-party 
effects.\463\ EEI includes voltage levels as another consideration that 
might be taken into account by transmission owners in their 
recommendation for transmission owners to study AAR implementation and 
propose candidate AAR transmission lines.\464\
---------------------------------------------------------------------------

    \462\ NRECA/LPPC Comments at 17.
    \463\ Entergy Comments at 10-11.
    \464\ EEI Comments at 7.
---------------------------------------------------------------------------

    222. LADWP requests flexibility in the implementation of AARs, 
noting high wind speeds in California increase wildfire risk and that 
it may be preferable to allow transmission line loadings to fall in 
those circumstances.\465\ PG&E, in proposing criteria for determining 
candidate transmission lines for AAR implementation, identifies 
wildfire risk and transmission lines within high fire threat districts 
as transmission lines that specifically may not be considered for AAR 
implementation.\466\ EEI includes wildfire areas as another 
consideration that might be taken into account by transmission owners 
in its recommendation for transmission owners to study AAR 
implementation and propose candidate AAR transmission lines.
---------------------------------------------------------------------------

    \465\ LADWP Comments at 6-7.
    \466\ PG&E Comments at 5.
---------------------------------------------------------------------------

    223. CAISO, SDG&E, and SCE also note challenges or the potential 
inapplicability of AARs to certain transmission lines under remedial 
action schemes.\467\ Given the challenges of applying AARs to remedial 
action schemes designed to prevent thermal overload, CAISO requests 
clarification on whether transmission lines whose thermal ratings 
trigger remedial action schemes should be rated using AARs.\468\ SCE 
explains that applying AARs to remedial action schemes, which are 
facility-rating dependent, may adversely impact the protection scheme, 
potentially increasing operational complexity, and could potentially 
initiate a widespread chain of additional reliability considerations 
that would require evaluation and potential mitigation.\469\ SDG&E also 
explains that it has flow-based remedial action schemes which use 
facility ratings to operate and are set to operate at a static value. 
According to SDG&E, all of these characteristics will cause AARs to 
yield no benefit to the monitored facilities and that removing this 
limitation will increase the complexity of the remedial action 
scheme.\470\
---------------------------------------------------------------------------

    \467\ SCE Comments at 4; SDG&E Comments at 4; CAISO Comments at 
12-13.
    \468\ CAISO Comments at 12-13.
    \469\ SCE Comments at 4.
    \470\ SDG&E Comments at 4.
---------------------------------------------------------------------------

    224. ISO-NE and NYISO also discuss remedial action schemes.\471\ 
NYISO discusses corrective action plans, which create plans to respond 
to contingencies, and voices concern that frequently updated 
transmission line ratings, especially an update that lowers 
transmission line ratings, would have a detrimental effect on 
reliability should the system operating limits used to develop the 
corrective action plan in planning studies not materialize in real 
time.\472\ ISO-NE requests that transmission lines where the actions or 
triggers of a remedial action scheme are based on a transmission line 
rating be exempt from any AAR requirement, noting that use of AARs on 
these transmission lines may require installing transmission system 
upgrades.\473\
---------------------------------------------------------------------------

    \471\ NYISO Comments at 7-8; ISO-NE Comments at 9.
    \472\ NYISO Comments at 7-8.
    \473\ ISO-NE Comments at 9.
---------------------------------------------------------------------------

    225. Exelon and EEI support the NOPR's proposed exceptions but 
request that the applicability of the exceptions be determined by the 
transmission owner, not the transmission provider.\474\ Exelon contends 
that because the NERC Reliability Standards give the transmission owner 
responsibility for establishing transmission facility ratings, the 
transmission owner should be the entity that decides when one or more 
of the exceptions apply.\475\
---------------------------------------------------------------------------

    \474\ Exelon Comments at 2; EEI Comments at 6.
    \475\ Exelon Comments at 11.
---------------------------------------------------------------------------

    226. Finally, EPSA asks that transmission providers be required to 
disclose (potentially via OASIS) which transmission lines they deem as 
not benefitting from an AAR or seasonal line rating. EPSA also asks 
that transmission providers be required to disclose the reasons for 
making those determinations to thereby enable RTOs/ISOs and market 
monitors to verify those decisions. Moreover, EPSA asks that these 
decisions be evaluated at least every five years to ensure AAR-exempt 
transmission lines should continue to qualify for exceptions.\476\
---------------------------------------------------------------------------

    \476\ EPSA Comments at 4.
---------------------------------------------------------------------------

3. Commission Determination
    227. As set forth in pro forma OATT Attachment M, we adopt the NOPR 
proposal to allow exceptions to the AAR and seasonal line rating 
requirements in instances where the transmission provider determines, 
consistent with good utility practice, that the transmission line 
rating of a transmission line is not affected by ambient air 
temperatures.\477\ In this instance, the transmission provider may use 
a transmission line rating for that transmission line that is not an 
AAR or seasonal line rating. Examples of such a transmission line may 
include (but are not limited to): (1) A transmission line for which the 
technical transfer capability of the limiting conductors and/or 
limiting transmission equipment is not dependent on ambient air 
temperatures; or (2) a transmission line whose transfer capability is 
limited by a transmission system limit (such as a system voltage or 
stability limit) which is not dependent on ambient air temperatures. As 
discussed in the NOPR, we adopt this exception because not all 
transmission line ratings are affected by ambient air temperature, 
either because the technical transfer capability of the limiting 
conductors and/or limiting transmission equipment is not dependent on 
ambient air temperature, or because the transmission line's transfer 
capability is limited by a transmission system limit (such as a system 
voltage or stability limit) which is not dependent on ambient air 
temperature.\478\
---------------------------------------------------------------------------

    \477\ As discussed in Section IV.B.2.b, we clarify that 
transmission owners, not transmission providers, are responsible for 
calculating transmission line ratings. However, in the RTO/ISO 
regions where there is a distinction between transmission owners and 
transmission providers, we clarify that we expect RTOs/ISOs to 
require their member transmission owners to make timely 
determinations on transmission line rating exceptions, and to 
provide them to the RTO/ISO. In such instances, we require the 
transmission provider to explain in its compliance filing, as part 
of its implementation of the new pro forma OATT Attachment M, 
through what mechanism (tariff, membership agreement, etc.) the 
transmission owner(s) will have the obligation for making and 
communicating to the transmission provider the timely determinations 
related to transmission line ratings exceptions.
    \478\ NOPR, 173 FERC ] 61,165 at P 103.
---------------------------------------------------------------------------

    228. We also adopt the NOPR proposal to establish a ``System 
Reliability'' section in pro forma OATT Attachment M that will allow a 
transmission provider to temporarily use a transmission line rating 
different than would otherwise be required under pro forma OATT 
Attachment M in instances when the transmission provider reasonably 
determines, consistent with good utility practice, that the use of such 
a temporary alternate rating is necessary to ensure the safety and 
reliability of the transmission system.\479\ As discussed in

[[Page 2280]]

the NOPR, while we expect that such alternate transmission line rating 
authority would be needed infrequently, if ever, we adopt the ``System 
Reliability'' section of pro forma OATT Attachment M to resolve any 
instance where a transmission provider reasonably believes that the 
requirements for transmission line ratings conflict with system safety 
or reliability.\480\
---------------------------------------------------------------------------

    \479\ Because the ``System Reliability'' section provides an 
exception and does not establish a requirement, we change the verb 
tense in this section to indicate that in such circumstances, the 
transmission provider may use an alternate transmission line rating 
rather than stating that the transmission provider ``will use'' an 
alternate transmission line rating as was proposed in the NOPR.
    \480\ NOPR, 173 FERC ] 61,165 at P 97.
---------------------------------------------------------------------------

    229. We decline to adopt the further specific exceptions requested 
by commenters. First, with respect to underground cables, as multiple 
commenters note, the transfer limit of underground cables is generally 
not affected by ambient air temperatures. Rather than adopting a 
blanket exception for underground transmission lines, we note that 
where the technical transfer limits of such cables are not affected by 
ambient air temperatures, they would satisfy the exception for 
instances in which the transmission line rating of a transmission line 
is not affected by ambient air temperatures. Because the transmission 
line ratings for underground transmission lines are generally the 
result of thermal issues in the oil-filled pipe, we agree with 
commenters that underground transmission lines likely satisfy such 
exception.
    230. With respect to older transmission facilities, we decline to 
adopt an exception from the AAR requirements for such facilities. We do 
not find the arguments that these facilities cannot be rated using AARs 
persuasive. For one, Reliability Standard FAC-008-5, which sets forth 
requirements to ensure that transmission line ratings used in 
operations are determined on a technically sound basis, makes no 
distinction with respect to age of transmission lines: Ratings for all 
transmission lines must be based on technically sound principles 
outlined in the Reliability Standard.\481\ Moreover, regardless of 
transmission facility age, the principles of transmission line sag and 
tension are correlated with the conductor material and construction 
style. A conductor's sag, tension, and swing properties are used to 
calculate clearances to vegetation, structures, and other distribution/
communication lines. For older transmission lines that do not have 
computerized sag/tension values, graphical methods can be used to 
generate the values.\482\ These values for older transmission lines, 
similar to parameters for new facilities, are used to calculate 
transmission line ratings and adjust transmission line ratings based on 
various operating/ambient air temperatures.
---------------------------------------------------------------------------

    \481\ In addition to the Reliability Standard, the NERC alert in 
2010 recommended that transmission owners conduct an assessment and 
perform any necessary remediation of rating issues including review 
of the current facility ratings methodology for their solely and 
jointly owned transmission lines to verify that the methodology used 
to determine facility ratings is based on actual field conditions 
with no distinguishment due to age of transmission assets.
    \482\ See, e.g., ``Sag-Tension Calculation Methods for Overhead 
Lines,'' CIGRE Task Force B2.12.3 (Apr. 2016); ``Graphic Method for 
Sag Tension Calculations for ACSR and Other Conductors,'' 
Publication No. 8, Aluminum Company of America (1961).
---------------------------------------------------------------------------

    231. Third, we decline to adopt a blanket exception from the AAR 
requirements for transmission facilities below a specific voltage 
threshold. Commenters have not explained why transmission line ratings 
from lower voltage transmission facilities cannot be rated using AARs. 
Rather, we find that the same principles and factors determining 
transmission line ratings for higher voltage transmission lines apply 
to lower voltage transmission line ratings. We further note that within 
RTOs/ISOs (and possibly in other areas), lower voltage transmission 
lines often represent the binding transmission constraints that cause 
congestion, because such lines are at their limits within the modeled 
contingencies, and so we expect that excluding such transmission lines 
would meaningfully reduce the benefits of AARs. However, in response to 
Entergy's comments,\483\ we note that in cases where lower voltage 
transmission facilities might host third-party under-build, such under-
build can and should be considered when developing the sag limits that 
inform a transmission facility's AARs.
---------------------------------------------------------------------------

    \483\ Entergy Comments at 10-11.
---------------------------------------------------------------------------

    232. Fourth, we decline to adopt a blanket exception for nomogram 
facilities, for transmission facilities that are part of certain 
remedial action schemes, or for transmission facilities in areas at 
risk of wildfires. For nomogram constraints, as noted in Section 
IV.B.1, these typically occur to protect system stability or voltage 
and the AAR requirements adopted herein exempt such transmission lines 
as well as those whose transmission line ratings that are not affected 
by ambient air temperatures. We also note that remedial action schemes 
are not inherently inconsistent with AAR implementation. For example, 
PJM implements both AARs and remedial action schemes.\484\ In any 
event, if the transmission owner determines that the transmission line 
ratings of transmission lines associated with the remedial action 
schemes are not affected by ambient air temperature because the 
operational limitations of the remedial action scheme represent the 
relevant limiting element, then the ``Exceptions'' paragraph of pro 
forma OATT Attachment M would apply. Moreover, the transmission 
provider may also utilize the ``System Reliability'' exception of pro 
forma OATT Attachment M if the reasonably transmission provider 
determines, consistent with good utility practice, that the temporary 
use of a transmission line rating different than would otherwise be 
required under pro forma OATT Attachment M is necessary to ensure 
safety and reliability. While we note the various exceptions to AAR 
implementation that may be applicable to remedial action schemes, we 
expect that, in situations where the remedial action scheme is not 
armed, transmission providers will implement the AAR requirements 
unless doing so would negatively impact system reliability. Finally, to 
mitigate the risk of wildfires, we reiterate our adoption of the 
``System Reliability'' exception in pro forma OATT Attachment M to 
ensure the safety and reliability of the transmission system. We 
believe this exception provides sufficient flexibility for transmission 
providers to use seasonal or static line ratings when reliability and 
good utility practice call for it.
---------------------------------------------------------------------------

    \484\ For example, PJM Manual 3: Transmission Operations, 
Attachment A, provides a listing of the remedial action schemes in 
operation in PJM. PJM Manual 3 is available here: https://pjm.com/-/media/documents/manuals/m03.ashx.
---------------------------------------------------------------------------

    233. As suggested by EPSA,\485\ we modify proposed pro forma OATT 
Attachment M to require transmission providers to reevaluate any 
exceptions taken under the ``Exceptions'' paragraph of pro forma OATT 
Attachment M at least every five years to ensure that longstanding 
exceptions continue to be valid. However, we clarify that if the 
technical basis for such an exception goes away, the transmission line 
must be re-rated in a timely manner,\486\ and that the five-year 
reevaluation requirement is just to ensure that any exceptions do not 
inadvertently grow

[[Page 2281]]

stale (i.e., the five-year reevaluation is not a justification for 
waiting five years to re-rate a transmission line). We do not 
specifically require a periodic re-evaluation of temporary alternate 
ratings, as we expect such ratings to be used over relatively short 
timeframes. However, we note that temporary alternate ratings may only 
be used during periods in which the transmission provider determines 
that they are necessary under the ``System Reliability'' section of pro 
forma OATT Attachment M.
---------------------------------------------------------------------------

    \485\ EPSA Comments at 4.
    \486\ The definition of transmission line rating we adopt in pro 
forma OATT Attachment M requires that transmission line ratings 
reflect the relevant technical limitations. Thus, when technical 
limitations that would justify an exception go away, that 
transmission line rating would need to be properly rated in a timely 
manner to continue to comply with the pro forma OATT.
---------------------------------------------------------------------------

    234. Finally, as further discussed below in Section IV.G.3.d, we 
modify proposed pro forma OATT Attachment M to require that uses of 
exceptions or temporary alternate ratings under pro forma OATT 
Attachment M be posted to OASIS or another password-protected website. 
We require that such postings document the nature of and basis for each 
such exception or alternate rating, as well as the date(s) and time(s) 
of initiation and (if applicable) withdrawal for the exception or the 
alternate rating. Further, transmission providers must maintain in such 
databases records of which transmission line ratings and methodologies 
were in effect at which times over at least the previous five years. 
This five-year period of record retention is consistent with a majority 
of the document retention periods required for OASIS postings.\487\
---------------------------------------------------------------------------

    \487\ 18 CFR 37.6 (Information to be posted on the OASIS).
---------------------------------------------------------------------------

E. Dynamic Line Ratings

1. Dynamic Line Ratings Definition
a. NOPR Proposal
    235. In the NOPR, the Commission proposed to define a dynamic line 
rating as a transmission line rating that applies to a time period of 
not greater than one hour and reflects up-to-date forecasts of inputs 
such as (but not limited to) ambient air temperature, wind, solar 
heating, transmission line tension, or transmission line sag.\488\
---------------------------------------------------------------------------

    \488\ NOPR, 173 FERC ] 61,165 at P 25.
---------------------------------------------------------------------------

b. Comments
    236. Comments on the proposed definition were limited; however, 
Industrial Customer Organizations ask that the proposed definition be 
expanded to include additional inputs, such as conductor temperature, 
thermal age of the line, and the cumulative number and frequency of 
faults. Industrial Customer Organizations assert that thermal age of a 
transmission line is a more accurate measure of a transmission line's 
physical capability than calendar age.\489\
---------------------------------------------------------------------------

    \489\ Industrial Customer Organizations Comments at 26.
---------------------------------------------------------------------------

    237. Noting that the Commission proposed to require AARs when 
evaluating requests for short-term transmission service and when 
considering potential curtailment, interruption, and/or redispatch 
expected to occur in the next 10 days, ACPA/SEIA argues that DLR 
implementation should also fulfill the AAR requirements in proposed pro 
forma OATT Attachment M.\490\
---------------------------------------------------------------------------

    \490\ ACPA/SEIA Comments at 12-13.
---------------------------------------------------------------------------

c. Commission Determination
    238. We adopt the definition of DLR that the Commission proposed in 
the NOPR. We believe that this definition clearly sets forth a non-
exhaustive list of factors affecting transmission line ratings to be 
input into calculations of DLRs. There are many factors that affect an 
individual transmission line rating; for this reason, it would be 
inappropriate for the Commission to attempt to create an exhaustive 
list of factors affecting transmission line ratings for inclusion in 
the definition of DLR.
    239. In response to arguments from ACPA/SEIA, we clarify that 
because the proposed addition to the Commission's regulations defines 
DLRs as reflecting up-to-date forecasts of ambient air temperature, 
along with other variables, and because pro forma OATT Attachment M and 
the Commission's regulations adopted in this final rule also define an 
AAR as reflecting up-to-date forecasts of ambient air temperature, 
implementing DLRs satisfies the requirements in pro forma OATT 
Attachment M to implement AARs.
2. DLR Requirements
a. NOPR Proposal
    240. In the NOPR, the Commission preliminarily found that between 
the two possible approaches to increasing transmission line rating 
accuracy--requiring AARs or requiring DLRs--an AAR requirement strikes 
a more appropriate balance between benefits and challenges than a DLR 
requirement. The Commission explained that, while DLRs can represent 
more accurate transmission line ratings than AARs, DLRs also present 
additional costs and challenges that AARs do not present. According to 
the Commission, these additional costs and challenges, relative to 
AARs, include placing sensors in remote locations, ensuring an 
appropriate level of cybersecurity, and various additional costs. 
Nevertheless, the Commission sought comment on whether to require 
transmission providers to implement DLRs across their transmission 
systems or on certain transmission lines that have the most to benefit 
from DLRs.\491\
---------------------------------------------------------------------------

    \491\ NOPR, 173 FERC ] 61,165 at P 100.
---------------------------------------------------------------------------

    241. Recognizing that DLRs have benefits in certain circumstances, 
the Commission proposed to require RTOs/ISOs to establish and implement 
the systems and procedures necessary to allow transmission owners to 
electronically update transmission line ratings (for each period for 
which transmission line ratings are calculated) at least hourly. Absent 
these capabilities, the Commission reasoned, the voluntary 
implementation of DLRs by transmission owners in some RTOs/ISOs would 
be of limited value, as their more dynamic ratings would not be 
incorporated into RTO/ISO markets.\492\ The Commission stated that it 
expected that many of the systems and procedures RTOs/ISOs would need 
to develop are likely to already be required as part of compliance with 
the proposed AAR requirements. Nonetheless, the Commission sought 
comment on the additional costs, if any, needed to comply with the 
proposed requirement that RTOs/ISOs also be able to accommodate 
frequently updated transmission line ratings from transmission 
owners.\493\
---------------------------------------------------------------------------

    \492\ NOPR, 173 FERC ] 61,165 at P 108.
    \493\ Id. P 109.
---------------------------------------------------------------------------

b. Comments
    242. Nearly all transmission owners that filed comments about DLRs 
either oppose a mandate to implement DLRs on all transmission lines 
\494\ or oppose a mandate in any form.\495\ Many of these transmission 
owners, as well as some RTOs/ISOs, see the merits of DLRs on some 
transmission lines, but only after taking into account transmission 
line characteristics that would make DLRs more or less cost 
effective.\496\
---------------------------------------------------------------------------

    \494\ APS Comments at 8; NYTOs Comments at 2; Indicated PJM 
Transmission Owners Comments at 13; PG&E Comments at 11-12.
    \495\ AEP Comments at 6; Dominion Comments at 9; Entergy 
Comments at 14; BPA Comments at 6; Exelon Comments at 3; PacifiCorp 
Comments at 5-6; NRECA/LPPC Comments at 3; MISO Transmission Owners 
Comments at 45-46; ITC Comments at 14-15.
    \496\ APS Comments at 8; Exelon Comments at 3, 13; PacifiCorp 
Comments at 5-6; EEI Comments at 15; ITC Comments at 12; AEP 
Comments at 6; NYTOs Comments at 4, 12-13; Dominion Comments at 9-
11; NYISO Comments at 5; PJM Comments at 10-11.
---------------------------------------------------------------------------

    243. In opposing a mandate to implement DLRs on all transmission 
lines, many transmission owners focus on the cost and challenges 
associated

[[Page 2282]]

with DLRs. Some offer rough quantitative estimates of these costs. For 
example, BPA explains that DLR implementation would require significant 
investment of potentially over $1 million per transmission line in 
monitoring equipment, software, and hardware to submit and host the 
data.\497\ MISO Transmission Owners explain that one transmission 
owner's experience with DLRs in MISO suggests that DLR implementation 
could cost between $100,000 and $200,000 per transmission line. MISO 
Transmission Owners assert that the cost to implement DLRs on all MISO 
transmission lines could be $1.5 billion (estimating $150,000 per line 
multiplied by 10,000 lines on the MISO system).\498\
---------------------------------------------------------------------------

    \497\ BPA Comments at 6.
    \498\ MISO Transmission Owners Comments at 47.
---------------------------------------------------------------------------

    244. Other transmission owners offer qualitative assessments of the 
potential costs and challenges associated with DLRs. APS asserts that 
DLRs are a high cost option with limited benefits.\499\ Exelon explains 
that any investment in DLRs could come at the expense of investment in 
other equipment.\500\ As EEI, Exelon, and NYTOs explain, there are 
additional costs and challenges associated with sensor and 
communication technology installation, cybersecurity, and with DLRs 
themselves, which tend to fluctuate.\501\ Entergy does not use DLRs and 
contends that DLRs present significant technical, logistical, and 
financial commitments, that the input data is too unpredictable, and 
that, while sensors work, they are not predictive of future 
conditions.\502\ Dominion also articulates concerns with DLR data 
interruptions.\503\ Others note the challenges associated with 
implementing DLRs on transmission lines traversing multiple temperature 
and wind climates.\504\ Finally, NYTOs note that, because AARs and DLRs 
are constantly changing, their use in real-time operations could lead 
to violations of NERC Reliability Standard FAC-008 if there are 
discrepancies, potentially caused by a software calculation error. 
NYTOs are concerned that there would be no allowance for time to 
identify any calculation errors. For this reason, NYTOs aver that 
independent software validation solutions would be needed.\505\
---------------------------------------------------------------------------

    \499\ APS Comments at 8.
    \500\ Exelon Comments at 16.
    \501\ EEI Comments at 15; Exelon Comments at 15-16; NYTOs 
Comments at 4.
    \502\ Entergy Comments at 14-15.
    \503\ Dominion Comments at 11.
    \504\ NYTOs Comments at 12; Exelon Comments at 14; BPA Comments 
at 6.
    \505\ NYTOs Comments at 7.
---------------------------------------------------------------------------

    245. Many transmission owners believe that DLRs have merit in 
certain applications, but argue that further study is needed. Some 
explain that they have experience with DLR pilot projects and limited 
DLR implementation and state that DLRs are likely economic in certain 
applications.\506\ For example, Dominion explains that it is currently 
analyzing three separate DLR pilot programs, but cautions that it is 
too early to judge the effectiveness of the technology.\507\ Potomac 
Economics and several transmission owners caution that the current 
focus should be on AAR implementation, not DLR implementation, and that 
the benefits of DLRs should be reassessed after AAR 
implementation.\508\ Sunflower does not rule out support for future DLR 
implementation, but states that DLRs must be thoroughly studied and 
tested first.\509\ Southern Company and NYTOs oppose implementation of 
either AARs or DLRs on all transmission lines. NYTOs instead suggest a 
compliance process to select transmission lines for either AAR or DLR 
implementation similar to the Order No. 1000 process for regional 
transmission planning, while Southern Company suggests that the 
Commission adopt a process similar to its ATC requirements and direct 
transmission providers to identify transmission facilities that would 
most benefit from both AAR and DLR implementation.\510\ While NRECA/
LPPC generally do not oppose using AARs and DLRs, they assert that 
consumer benefits in the form of lower costs should remain the primary 
focus, so long as safety and reliability are uncompromised. 
Furthermore, NRECA/LPPC argue that conservative transmission line 
ratings of facilities must continue to account for unanticipated 
conditions and human error.\511\
---------------------------------------------------------------------------

    \506\ EEI Comments at 15; ITC Comments at 12; AEP Comments at 6; 
Exelon Comments at 13; APS Comments at 8; NYTOs Comments at 4, 12-
13; Dominion Comments at 9-11.
    \507\ Dominion Comments at 4.
    \508\ Potomac Economics Comments at 20; ITC Comments at 14-15; 
PG&E Comments at 11-12; NYTOs Comments at 13.
    \509\ Sunflower Comments at 5-6.
    \510\ NYTOs Comments at 10; Southern Company Comments at 2-3.
    \511\ NRECA/LPPC Comments at 7-8.
---------------------------------------------------------------------------

    246. Similarly, RTOs/ISOs caution that a full DLR mandate is 
premature \512\ and some argue that the decision to study or pursue 
DLRs should be left to transmission owners.\513\ PJM asserts that RTOs/
ISOs could rank the most congested transmission lines, which might 
serve to test the degree to which such transmission lines might be 
impacted by DLR implementation, and asserts that DLRs should only be 
used on the most congested transmission lines.\514\ SPP believes that 
the DLR implementation costs to transmission owners may outweigh the 
benefits, estimating that DLR implementation that requires an EMS 
upgrade would cost transmission owners up to $1 million and, without 
upgrading the EMS, DLR implementation would cost an additional 
$100,000-$500,000 annually in additional SCADA communications with the 
Reliability Coordinator's EMS.\515\ ISO-NE notes that transmission 
lines in its territory often do not follow a linear path, which can 
result in different transmission line ratings for different segments of 
the same transmission line at the same time if wind speed is taken into 
account rather than solely ambient air temperature.\516\ NYISO explains 
that its currently-effective DLR functionality and seasonal 
transmission line ratings ``support effective system planning, 
efficient markets, reliable system operation, and the flexibility 
needed for NYISO and TO operators to respond to real-time system 
conditions''; \517\ however, this has historically been used to 
increase transmission line ratings in real time based on ambient 
conditions. NYISO voices concern that frequently updated transmission 
line ratings, especially those that lower transmission line ratings in 
real-time during emergency conditions, would have a detrimental effect 
on reliability in the context of corrective action plans designed to 
create plans to respond to contingencies, should the system operating 
limits used to develop the corrective action plan be lowered in real 
time.\518\ NYISO further explains that instances wherein increased 
transmission line ratings in the day-ahead market resulting in 
increased commitments are then reduced in the real-time markets could 
increase uplift costs.\519\
---------------------------------------------------------------------------

    \512\ CAISO Comments at 16; ISO-NE Comments at 12; NYISO 
Comments at 7; PJM Comments at 10-11; MISO Comments at 33.
    \513\ CAISO Comments at 16; PJM Comments at 10-11,13; MISO 
Comments at 33.
    \514\ PJM Comments at 12.
    \515\ SPP Comments at 12.
    \516\ ISO-NE Comments at 19.
    \517\ NYISO Comments at 6.
    \518\ Id. at 7-8.
    \519\ Id. at 14.
---------------------------------------------------------------------------

    247. The market monitors are divided over the timing and 
implementation of a DLR mandate. The SPP MMU recommends DLR 
implementation on all transmission lines, not just congested 
transmission lines, to account for the interlinkage among transmission 
lines

[[Page 2283]]

and to avoid preferential treatment or gaming of transmission lines 
selected for DLR.\520\ On the other hand, Potomac Economics suggests 
further study and discourages mandates for both universal and targeted 
DLR implementation at this time.\521\ The CAISO DMM states that it 
would support the use of DLRs where practicable in the future and 
suggests that conservative assumptions for some applications, such as 
in the day-ahead market or future advisory intervals, may be 
appropriate. As such, the CAISO DMM requests that RTOs/ISOs retain the 
ability to adjust modeled transmission for reliability.\522\
---------------------------------------------------------------------------

    \520\ SPP MMU Comments at 4.
    \521\ Potomac Economics Comments at 20.
    \522\ CAISO DMM Comments at 2-3.
---------------------------------------------------------------------------

    248. State agencies, consumer advocacy groups, and other 
miscellaneous organizations generally support DLR implementation, but 
vary widely on what approach the Commission should take. Some groups 
support the Commission requiring full DLR implementation. R Street 
Institute contends that DLRs should be required by default, with 
exception given when justified by a cost-benefit analysis.\523\ 
Industrial Customer Organizations likewise contend that the Commission 
should require the implementation of DLRs unless a transmission owner 
can establish that costs would exceed benefits to consumers.\524\ ACORE 
recommends the Commission take further steps to encourage DLR 
deployment.\525\ Clean Energy Parties argue that DLR is superior to 
AAR, and that the Commission should establish criteria for when DLR is 
required.\526\ ACPA/SEIA contend that DLR can provide significant 
benefits,\527\ and that congestion reviews should evaluate both AARs 
and DLRs for any congested transmission line.\528\
---------------------------------------------------------------------------

    \523\ R Street Institute Comments at 3.
    \524\ Industrial Customer Organizations Comments at 5.
    \525\ ACORE Comments at 1.
    \526\ Clean Energy Parties Comments at 5, 7.
    \527\ ACPA/SEIA Comments at 5-6.
    \528\ Id. at 9-11.
---------------------------------------------------------------------------

    249. Several groups also argue for more targeted or limited DLR 
requirements. WATT proposes a list of criteria for requiring DLR 
implementation,\529\ and contends that such criteria can help overcome 
concern about costs exceeding benefits.\530\ ACPA/SEIA similarly 
support requiring an evaluation of both AARs and DLRs for any congested 
transmission line, and a DLR requirement where appropriate.\531\ EDFR 
supports requiring DLRs when cost-benefit analysis or public policy 
justifies their use.\532\ EPSA contends that the Commission should 
first require DLRs only on transmission lines that are deemed to be the 
most critical for optimizing system performance.\533\ Vistra states 
that it uses DLRs with some of its facilities in ERCOT, and states that 
it has seen improved congestion management, greater deliverability of 
low-cost energy to load, lower costs for load, higher revenues for low 
cost remote generation, and lower hedging costs.\534\ Vistra states 
that DLR benefits will become increasingly important as more zero 
marginal cost energy resources are added to the resource mix.\535\
---------------------------------------------------------------------------

    \529\ WATT proposes for sensor-based DLR to be required on all 
thermally limited transmission lines rated 69 kV or greater when 
market congestion totaling over $1 million has occurred within the 
past year; the transmission line is identified as being a constraint 
projected to have market congestion over $1 million over the coming 
three years as a part of the current RTO/ISO transmission planning 
cycle process, which can be economic or reliability based; thermally 
limited transmission lines show up as limiting in generator 
interconnection system impact studies; or generation curtailed by 
more than 10% on average for one year due to factors that include 
transmission line capacity. WATT Comments at 10.
    \530\ Id. at 2, 10-11.
    \531\ ACPA/SEIA Comments at 8-10.
    \532\ EDFR Comments at 4.
    \533\ EPSA Comments at 6.
    \534\ Vistra Comments at 2-3.
    \535\ Id. at 3.
---------------------------------------------------------------------------

    250. Several other groups support DLR mandates or oversight of 
voluntary deployment. TAPS supports voluntary implementation of DLRs, 
but also argues that subjective deployment decisions should be subject 
to monitoring.\536\ Industrial Customer Organizations contend that the 
Commission should, at minimum, require the implementation of staggered 
pilot programs requiring the implementation of DLRs on the most 
thermally limited, congested transmission lines.\537\ Certain TDUs 
argue that DLR utilization can improve contingency planning and defer 
or eliminate the need for transmission line upgrades or 
reconductoring.\538\
---------------------------------------------------------------------------

    \536\ TAPS Comments at 15-17.
    \537\ Industrial Customer Organizations Comments at 25.
    \538\ Certain TDUs Comments at 6-7.
---------------------------------------------------------------------------

    251. In response to the Commission's proposal to require RTOs/ISOs 
to establish and implement the systems and procedures necessary to 
allow transmission owners to electronically update transmission line 
ratings (for each period for which transmission line ratings are 
calculated) at least hourly, however, commenters are broadly 
supportive. For example, PacifiCorp agrees with the Commission that 
many of the systems and procedures RTOs/ISOs would need to develop to 
accept DLRs are likely to already be required as part of compliance 
with the requirements to adopt AARs.\539\ PJM notes that, as part of 
DLR pilot projects, it has received and reviewed DLRs.\540\ Similarly, 
NYISO notes that it has successfully implemented DLR functionality to 
allow asset owners to increase real-time transmission line capability, 
when appropriate, and notes that this implementation does not 
differentiate between AARs and DLRs.\541\
---------------------------------------------------------------------------

    \539\ PacifiCorp Comments at 6.
    \540\ PJM Comments at 11-12.
    \541\ NYISO Comments at 4.
---------------------------------------------------------------------------

c. Commission Determination
    252. Based on the record, we decline to mandate DLR implementation 
in this final rule.
    253. We agree with commenters that highlight the benefits to DLR 
implementation.\542\ For example, use of DLRs generally allows for 
greater power flows than would otherwise be allowed, and its use can 
also detect situations where power flows should be reduced to maintain 
safe and reliable operation and avoid unnecessary wear on transmission 
equipment.\543\ We agree with EPSA, which, citing to a PJM pilot 
program with AEP and PPL Electric Utilities Corporation, explains that 
there could be significant benefits to strategically expanding DLR 
deployment.\544\ Additionally, we agree with Exelon that there may be 
targeted applications in which DLRs can provide net benefits to 
customers. For example, when the limiting element for a transmission 
facility experiencing significant congestion is the conductor and 
conditions besides ambient air temperature have a consistent and 
significant impact on the power carrying capabilities of the line, DLRs 
may provide more accurate transmission line ratings than AARs and 
therefore may provide significant benefits.\545\
---------------------------------------------------------------------------

    \542\ Clean Energy Parties Comments at 6; EPSA Comments at 5; 
Exelon Comments at 13.
    \543\ Clean Energy Parties Comments at 6.
    \544\ EPSA Comments at 5.
    \545\ Exelon Comments at 13.
---------------------------------------------------------------------------

    254. However, we appreciate that while DLRs can represent more 
accurate transmission line ratings than AARs, DLR implementation also 
presents additional costs and challenges not found in AAR 
implementation. Relative to AARs, these additional costs and challenges 
include placing sensors in remote locations, ensuring the cybersecurity 
of sensors, and various additional costs. The record in this proceeding 
is not sufficient for the Commission to evaluate the relative benefits 
and costs and challenges of DLR implementation. For this reason,

[[Page 2284]]

we incorporate the record in this proceeding on DLRs into new Docket 
No. AD22-5-000, which we open to further explore DLR implementation.
    255. Finally, we adopt the Commission's proposal in the NOPR to 
require RTOs/ISOs to establish and maintain systems and procedures 
necessary to allow transmission owners to electronically update 
transmission line ratings (for each period for which transmission line 
ratings are calculated) at least hourly, with such data submitted by 
transmission owners directly into the RTO's/ISO's EMS through SCADA or 
related systems.\546\ We continue to find that, because DLR 
implementation may be economic in certain applications,\547\ absent 
RTOs/ISOs having these capabilities, voluntary implementation of DLRs 
by transmission owners in some RTOs/ISOs would be of limited value, as 
their more dynamic ratings and resulting benefits would not be 
incorporated into RTO/ISO markets. Absent these minimum capabilities, 
RTO/ISO software would serve as a barrier that prevents transmission 
owners in RTOs/ISOs from implementing DLRs that can better reflect the 
actual transfer capability of the transmission system and, 
consequently, wholesale rates would not remain just and reasonable. 
Additionally, as the Commission stated in the NOPR, we continue to 
expect that many of the systems and procedures RTOs/ISOs would need to 
develop to accept DLRs are likely to already be required as part of 
compliance with the AAR requirements adopted in this final rule.
---------------------------------------------------------------------------

    \546\ However, we add the DLR requirement adopted herein to 18 
CFR 35.28(g)(13), rather than to 18 CFR 35.28(g)(12) as proposed in 
the NOPR, in light of the requirements recently approved in Order 
No. 2222. See Participation of Distributed Energy Resource 
Aggregations in Markets Operated by Regional Transmission 
Organizations and Independent System Operators, Order No. 2222, 85 
FR 68450 172 FERC ] 61,247 (2020), order on reh'g, Order No. 2222-A, 
174 FERC ] 61,197 (2021).
    \547\ EEI Comments at 15; ITC Comments at 12; AEP Comments at 6; 
Exelon Comments at 13; APS Comments at 8; NYTOs Comments at 4, 12-
13; Dominion Comments at 9-11.
---------------------------------------------------------------------------

3. Extending to Non-RTO/ISO Transmission Providers the Requirement To 
Allow Transmission Owners To Electronically Update Transmission Line 
Ratings at Least Hourly
a. NOPR Proposal
    256. In addition to requiring RTOs/ISOs to establish and implement 
the systems and procedures necessary to allow transmission owners to 
electronically update transmission line ratings at least hourly, the 
Commission also sought comment on whether there is any need to extend 
this same requirement to transmission providers that operate outside of 
an RTO/ISO.\548\
---------------------------------------------------------------------------

    \548\ NOPR, 173 FERC ] 61,165 at P 109.
---------------------------------------------------------------------------

b. Comments
    257. Comments on this question are limited. EEI and PacifiCorp 
state that there is no need to extend this requirement beyond RTOs/
ISOs.\549\ R Street Institute, however, observes that transmission 
management inefficiency and transmission line rating opacity outside 
RTOs/ISOs is far greater than within RTOs/ISOs, and therefore concludes 
that updating transmission line ratings hourly outside RTOs/ISOs would 
be a prudent start.\550\ Similarly, WATT argues that the same 
requirements should apply consistently across RTOs/ISOs and non-RTOs/
ISOs, noting concerns of utilities considering voluntary RTO/ISO 
membership that regulatory requirements are stricter within RTOs/ISOs 
than outside RTOs/ISOs which serves as a disincentive to RTO/ISO 
participation.\551\
---------------------------------------------------------------------------

    \549\ EEI Comments at 18-19; PacifiCorp Comments at 6.
    \550\ R Street Institute Comments at 5.
    \551\ WATT Comments at 15.
---------------------------------------------------------------------------

c. Commission Determination
    258. We decline to extend the requirement for RTOs/ISOs to be able 
to accept DLRs to non-RTO/ISO transmission providers at this time. As 
EEI explains, in most cases outside of an RTO/ISO market, transmission 
providers operate only their own transmission systems. In those cases, 
transmission providers have the ability to fully implement DLRs should 
they choose to do so. Because non-RTO/ISO transmission providers are 
also typically the transmission owner, we find that any requirement for 
non-RTO/ISO transmission providers to be able to accept DLRs would be 
unnecessary.
4. DLR Studies
a. NOPR Proposal
    259. In the NOPR, the Commission sought comment on whether to 
require RTOs/ISOs to conduct a one-time study of the cost effectiveness 
of DLR implementation, and if so, what details/format any such study 
should include.\552\
---------------------------------------------------------------------------

    \552\ NOPR, 173 FERC ] 61,165 at P 110.
---------------------------------------------------------------------------

b. Comments
    260. Most transmission owners oppose requirements for RTOs/ISOs to 
study the cost effectiveness of DLR implementation.\553\ One exception 
is PG&E, which argues that an RTO/ISO study could identify the efficacy 
of system-wide DLR implementation relative to more localized use.\554\ 
Exelon opposes a study requirement, asserting that it would be costly, 
time-consuming, and duplicative to existing processes.\555\ Indicated 
PJM Transmission Owners contend that there would be little point in PJM 
conducting another DLR study and caution that any DLR study would be 
costly and highly locational in nature, possibly necessitating DLR 
sensor installation.\556\ MISO Transmission Owners question whether the 
RTO/ISO is the appropriate entity to study the cost effectiveness of 
DLR implementation and further explain that certain study details 
remain unaddressed.\557\ Therefore, MISO Transmission Owners assert 
that the Commission should provide flexibility for transmission owners 
and RTOs/ISOs to collaborate on a voluntary basis to conduct DLR 
studies.\558\ EEI also does not support a mandate to study DLR cost 
effectiveness, explaining that RTOs/ISOs already study congestion and 
solutions to resolve congestion in the transmission planning 
processes.\559\ Dominion cautions that, should the Commission require 
DLR studies, such studies should involve transmission owners.\560\ 
Finally, Certain TDUs explain that transparency into the benefits of 
DLRs is important, and they therefore support DLR studies, but argue 
that studies should involve the RTOs/ISOs and be incorporated into the 
transmission planning processes.\561\
---------------------------------------------------------------------------

    \553\ MISO Transmission Owners Comments at 38; ITC Comments at 
15; Exelon Comments at 6; Dominion Comments at 12; EEI Comments at 
16; Indicated PJM Transmission Owners Comments at 13-14.
    \554\ PG&E Comments at 11.
    \555\ Exelon Comments at 6.
    \556\ Indicated PJM Transmission Owners Comments at 13-14.
    \557\ Specifically, MISO Transmission Owners explain that the 
Commission should clarify for what purpose the study results would 
be used.
    \558\ MISO Transmission Owners Comments at 38.
    \559\ EEI Comments at 16.
    \560\ Dominion Comments at 12.
    \561\ Certain TDUs Comments at 7.
---------------------------------------------------------------------------

    261. Several RTOs/ISOs also discourage the Commission from 
requiring DLR studies.\562\ MISO states that studies should be 
transmission line specific and driven by the transmission owners.\563\ 
ISO-NE does not believe a study is necessary until, and unless, AARs 
are fully implemented. ISO-NE recommends that, if a study is required, 
it be carried out by a third party.\564\ CAISO opposes DLR cost-
effectiveness study requirements but would not

[[Page 2285]]

oppose an informational report on its work with stakeholders evaluating 
the costs and benefits of DLRs.\565\ PJM argues that several 
outstanding issues should be studied and recommends: (1) Periodic 
reporting requirements by region on the status and lessons learned from 
DLR deployments; (2) requiring transmission owners to document their 
DLR implementation processes; and (3) technical conferences to share 
best practices on DLR implementation.\566\ SPP notes that it recently 
published a whitepaper that examined the costs and benefits of 
DLRs.\567\
---------------------------------------------------------------------------

    \562\ CAISO Comments at 16; ISO-NE Comments at 12; MISO Comments 
at 33.
    \563\ MISO Comments at 33.
    \564\ ISO-NE Comments at 12.
    \565\ CAISO Comments at 16.
    \566\ PJM Comments at 13-14.
    \567\ SPP Comments at 15.
---------------------------------------------------------------------------

    262. EPRI argues that, before studies on DLR cost effectiveness can 
be conducted, studies on monitoring systems must be conducted. 
According to EPRI, such studies must identify a technical basis to 
select sensors, establish the accuracy of sensors, develop an 
understanding of sensors' reliability and maintenance needs, and 
identify methods to integrate monitoring system data into an EMS. EPRI 
states that unbiased information on monitoring systems is not yet 
available and explains that some commercial DLR monitoring equipment 
may not be up to utility standards.\568\
---------------------------------------------------------------------------

    \568\ EPRI Comments at 5.
---------------------------------------------------------------------------

    263. While RTOs/ISOs and transmission owners generally oppose a 
study requirement, several commenters are more supportive of DLR study 
requirements. New England State Agencies support independent studies on 
the cost-effectiveness of DLRs as a first step before ordering 
implementation.\569\ Ohio FEA does not support Commission requirements 
for RTOs/ISOs to study the cost effectiveness of DLR implementation, 
but, noting that DLRs may be cost effective on certain lines, states 
that pilot programs should be initiated to identify these segments 
through the stakeholder process rather than a requirement.\570\ CEA 
supports DLR feasibility studies to address the cost of infrastructure 
and EMS-SCADA changes, the challenges of implementing DLRs on 
transmission lines with varying climates and little communications 
infrastructure, and DLR forecasting challenges, but questions whether 
risks and costs will be borne by RTOs/ISOs or by transmission 
owners.\571\ Clean Energy Parties support requiring RTOs/ISOs to 
conduct a study of the cost effectiveness of DLR implementation.\572\ 
OMS contends that industry and regulators need more information to 
better understand the potential benefits of DLRs.\573\
---------------------------------------------------------------------------

    \569\ New England State Agencies Comments at 14.
    \570\ Ohio FEA Comments at 6-7.
    \571\ CEA Comments at 2-3.
    \572\ Clean Energy Parties Comments at 11.
    \573\ OMS Comments at 12.
---------------------------------------------------------------------------

c. Commission Determination
    264. In consideration of the comments on this issue, we decline to 
require one-time DLR studies at this time. We agree with New England 
State Agencies and OMS that studies assessing the cost effectiveness of 
DLR implementation may be useful to transmission providers in 
identifying possible transmission line candidates for DLR deployment 
and serve as a good first step prior to consideration of additional 
requirements.\574\ Specifically, such studies may support the 
development of various criteria transmission providers could use to 
identify candidates for DLR deployment.\575\ However, we also agree 
that there are various factors to consider in order to determine when 
and how such studies should be conducted, including whether such 
studies: Should be conducted by independent third parties; should 
incorporate the adoption of AARs into the analysis; \576\ and would 
overlap with existing congestion studies in RTOs/ISOs.\577\ Although we 
decline to require one-time DLR studies at this time, we incorporate 
the record in this proceeding on DLRs into new Docket No. AD22-5-000, 
which we open to further explore DLR implementation.
---------------------------------------------------------------------------

    \574\ New England State Agencies Comments at 14; OMS Comments at 
12.
    \575\ WATT Comments at 10; ACPA/SEIA Comments at 9-10; Clean 
Energy Parties Comments at 7-10.
    \576\ ISO-NE Comments at 11-12.
    \577\ EEI Comments at 16; Exelon Comments at 6.
---------------------------------------------------------------------------

5. Advanced Transmission Technology Cost Recovery
a. Comments
    265. ENEL states that advanced transmission technologies can 
achieve cost savings and provide value to ratepayers, such that 
transmission owners should be eligible to recover their costs through 
rate base and to earn a return, and requests clarification on the cost 
allocation and recovery associated with AAR and DLR 
implementation.\578\
---------------------------------------------------------------------------

    \578\ ENEL Comments at 2-3.
---------------------------------------------------------------------------

b. Commission Determination
    266. We are not considering in this proceeding whether to grant 
special rate treatment for technologies used to implement AARs and 
DLRs. We are also not considering in this proceeding whether to change 
the Commission's policies regarding cost recovery. While the purchase 
and installation cost of equipment that may normally be considered as 
plant in service may be eligible for inclusion in rate base, without 
knowing the specific facts related to a particular investment, it would 
be impractical to address their cost recovery at this time. However, 
once specific costs are known, parties can file with the Commission to 
seek recovery, as appropriate.\579\
---------------------------------------------------------------------------

    \579\ Note that the Commission convened a workshop on September 
10, 2021, to discuss certain performance-based ratemaking 
approaches, particularly shared savings, that may foster deployment 
of transmission technologies. Notice of Workshop, Docket Nos. AD19-
19-000, RM20-10-000 (Apr. 15, 2021).
---------------------------------------------------------------------------

F. Emergency Ratings

1. NOPR Request for Comments
    267. In the NOPR, the Commission sought comment on: (1) Whether to 
require transmission providers to use unique emergency ratings; (2) the 
degree to which transmission providers use or are provided with unique 
emergency ratings and the emergency rating durations that are commonly 
used; (3) whether and how requirements to implement unique emergency 
ratings would impact the useful life of transmission equipment; and (4) 
the feasibility of calculating emergency ratings on transmission 
equipment other than conductors and transformers.\580\ The Commission 
stated that emergency ratings should not be arbitrarily set equal to 
normal ratings, but rather should be developed from appropriate, unique 
technical inputs.\581\ The Commission acknowledged that there may be 
some instances when, after a proper technical analysis considering the 
relevant rating timeframes, the emergency rating is equal to the normal 
rating.\582\
---------------------------------------------------------------------------

    \580\ NOPR, 173 FERC ] 61,165 at PP 111-113.
    \581\ Id. P 110.
    \582\ Id. P 46 n.57.
---------------------------------------------------------------------------

    268. The Commission observed that, for short periods of time, most 
transmission equipment can withstand high currents without sustaining 
damage, which allows transmission owners to develop two sets of ratings 
for most facilities: Normal ratings that can be safely used 
continuously (i.e., not time-limited) and emergency ratings that can be 
safely used for a limited period of time. Whether and how a 
transmission owner establishes emergency ratings is important because 
emergency ratings are a critical input into determining operating 
limits in market models, both during normal operations and during post-
contingency operations. Market models often allow

[[Page 2286]]

post-contingency flows on transmission lines to exceed normal ratings 
for short periods of time, as long as the flows do not exceed the 
applicable emergency rating for the corresponding timeframe. Because 
these emergency ratings are a more accurate representation of the flow 
limits over shorter timeframes, their use in models of post-contingency 
flows may produce prices which more accurately reflect actual costs to 
delivering wholesale energy to transmission customers. Since the 
transmission system is operated to withstand contingencies, the use of 
unique emergency ratings, where appropriate, allows for greater flows 
during normal conditions as well. The Commission further stated that 
this greater transfer capability can provide significant cost savings 
and afford transmission providers additional flexibility in how to 
respond to unforeseen events.\583\ Noting the potential negative 
consequences of emergency ratings, however, the Commission recognized 
concerns that the use of emergency ratings could impact reliability by 
degrading affected transmission facilities and ultimately reducing the 
equipment's useful life.\584\
---------------------------------------------------------------------------

    \583\ Id. P 112.
    \584\ Id. P 113.
---------------------------------------------------------------------------

2. Emergency Ratings Definition and Implementation Requirements
a. Comments
    269. Some transmission owners oppose a potential mandate to require 
unique emergency ratings,\585\ while others do not oppose the use of 
emergency ratings, but oppose a mandate, asking for flexibility to 
determine how and when to use emergency ratings.\586\ Some transmission 
owners note that they use emergency ratings on their systems,\587\ 
while several of these support the use of emergency ratings.\588\ PG&E, 
for example, notes that it currently uses emergency ratings for both 
planning and real-time operations.\589\ APS states that the use of 
emergency ratings gives operators sufficient time to respond and 
supports their use during post-contingency operations for a 30-minute 
timeframe.\590\ Tangibl notes that PJM's experience shows that 
implementation and use of unique emergency ratings is longstanding and 
feasible.\591\
---------------------------------------------------------------------------

    \585\ Dominion Comments at 12; EEI Comments at 16-17; MISO 
Transmission Owners Comments at 17; NRECA/LPPC Comments at 25-26; 
Southern Company Comments at 4.
    \586\ See, e.g., EEI Comments at 16-17; SDG&E Comments at 4-5. 
Exelon and ITC, while not opposing or supporting a mandate for the 
use of emergency ratings, similarly contend that transmission owners 
should be responsible for calculating emergency ratings and 
determining the facilities for which they are appropriate. Exelon 
Comments at 19-20; ITC Comments at 12.
    \587\ APS Comments at 7; Dominion Comments at 4; Entergy 
Comments at 1; EEI Comments at 16; Exelon Comments at 22; Indicated 
PJM Transmission Owners Comments at 2; PacifiCorp Comments at 4; 
PG&E Comments at 12; SDG&E Comments at 3; WAPA Comments at 8.
    \588\ APS Comments at 7; Dominion Comments at 4; Exelon Comments 
at 22; Indicated PJM Transmission Owners Comments at 15; PacifiCorp 
Comments at 4.
    \589\ PG&E Comments at 12.
    \590\ APS Comments at 7.
    \591\ Tangibl Comments at 4.
---------------------------------------------------------------------------

    270. Four RTOs/ISOs indicate that they use emergency ratings.\592\ 
RTOs/ISOs are evenly divided on potential requirements to calculate and 
implement emergency ratings. CAISO and MISO oppose an emergency rating 
mandate. CAISO believes that there is no need for a mandate since it 
already maintains emergency ratings in the CAISO register of 
transmission and facility line ratings; MISO argues that any such 
mandate, if directed, should be to transmission owners.\593\ Of the 
RTOs/ISOs in support of potential emergency ratings requirements, ISO-
NE recognizes the benefits resulting from their use and NYISO is 
supportive so long as the equipment supports the transmission line 
rating.\594\
---------------------------------------------------------------------------

    \592\ CAISO Comments at 1; NYISO Comments at 3; ISO-NE Comments 
at 6; MISO Comments at 25.
    \593\ CAISO Comments at 15; MISO Comments at 24-25 & n.45.
    \594\ NYISO Comments at 14 n.13; ISO-NE Comments at 10.
---------------------------------------------------------------------------

    271. Market monitors, independent agencies, technical experts, 
renewable energy advocates, generation companies, and load all 
generally support the use of unique emergency ratings \595\ and most 
support requirements for their use.\596\ The SPP MMU and Potomac 
Economics support requiring transmission providers to establish 
emergency ratings using unique technical inputs that are separate from 
normal ratings.\597\ Potomac Economics notes that transmission owners 
will not voluntarily adopt broad or consistent emergency ratings use 
without a requirement.\598\ Industrial Customer Organizations state 
that the need for accurate transmission line ratings applies especially 
during emergency operations.\599\ Tangibl contends that a spot check of 
facilities in PJM shows that almost all have unique emergency 
ratings.\600\
---------------------------------------------------------------------------

    \595\ ACPA/SEIA Comments at 17; EDFR Comments at 6; Industrial 
Customer Organizations Comments at 27; R Street Institute Comments 
at 3; Tangibl Comments at 2; WATT Comments at 13 (supported in 
general by LineVision).
    \596\ EDFR Comments at 6; Potomac Economics Comments at 4; R 
Street Institute Comments at 3; SPP MMU Comments at 5; Tangibl 
Comments at 2; WATT Comments at 13 (supported in general by 
LineVision).
    \597\ Potomac Economics Comments at 4; SPP MMU Comments at 5.
    \598\ Potomac Economics Comments at 4.
    \599\ Industrial Customer Organizations Comments at 27.
    \600\ Tangibl Comments at 3.
---------------------------------------------------------------------------

    272. Many transmission owners emphasize that emergency ratings can 
be the same as the normal rating \601\ and state the importance of 
transmission owner discretion in setting emergency ratings.\602\ MISO 
and CAISO oppose any unique emergency ratings mandate, claiming that 
good reasons may exist to justify their not being unique.\603\ CAISO, 
NYISO, and MISO provide examples of cases where emergency ratings could 
be the same as the normal rating for a transmission facility.\604\ 
Recognizing these cases, CAISO requests that any final rule requiring 
unique emergency ratings allow for and appropriately account for 
exceptions.\605\ The SPP MMU and Potomac Economics support requiring 
transmission providers to establish emergency ratings using unique 
technical inputs that are separate from normal ratings.\606\
---------------------------------------------------------------------------

    \601\ See, e.g., Entergy Comments at 4; Exelon Comments at 19-
20; ITC Comments at 3; MISO Transmission Owners Comments at 17; 
NRECA/LPPC Comments at 25; SDG&E Comments at 4.
    \602\ See, e.g., EEI Comments at 16-17; Exelon Comments at 19-
20; ITC Comments at 12; MISO Transmission Owners Comments at 40-41; 
Indicated PJM Transmission Owners Comments at 15; SDG&E Comments at 
4-5.
    \603\ CAISO Comments at 15; MISO Comments at 24-25.
    \604\ CAISO Comments at 15; NYISO Comments at 14 n.13; MISO 
Comments at 24-25.
    \605\ CAISO Comments at 15.
    \606\ SPP MMU Comments at 5; Potomac Economics Comments at 4.
---------------------------------------------------------------------------

    273. ITC and MISO Transmission Owners argue that requiring unique 
emergency ratings could create a perverse incentive for normal ratings 
to be revised downward so that there can be unique emergency 
ratings.\607\ Similarly, MISO argues that it is sub-optimal to 
artificially lower the normal ratings to create the appearance of a 
deviation from the emergency rating when they would otherwise be 
equal.\608\ MISO Transmission Owners assert that requiring emergency 
ratings that are unique from normal ratings is unnecessary and 
arbitrary.\609\
---------------------------------------------------------------------------

    \607\ ITC Comments at 12; MISO Transmission Owners Comments at 
17; MISO Comments at 25.
    \608\ MISO Comments at 25.
    \609\ MISO Transmission Owners Comments at 40.
---------------------------------------------------------------------------

    274. MISO states that the NOPR appears to regard cases where 
transmission lines have equal emergency and normal ratings as 
exceptional although they may occur regularly.\610\ MISO Transmission

[[Page 2287]]

Owners read the NOPR as suggesting that having the same rating for 
normal and emergency operations reflects a lack of effort by 
transmission owners to analyze and incorporate appropriate emergency 
ratings.\611\ According to MISO Transmission Owners, it would not be 
problematic for the Commission to require separate normal and emergency 
ratings on facilities where transmission owners determine they are 
appropriate.\612\ Similarly, MISO argues that transmission owners 
should evaluate a facility's normal and emergency capability separately 
and distinctly where each transmission line rating fully uses the 
technical capabilities of the installed equipment considering good 
utility practice, sound engineering judgment, manufacturer guidance, 
and equipment reliability experience for each rating type.\613\
---------------------------------------------------------------------------

    \610\ MISO Comments at 25.
    \611\ MISO Transmission Owners Comments at 17.
    \612\ Id. at 40.
    \613\ MISO Comments at 25-26.
---------------------------------------------------------------------------

    275. The SPP MMU states that there may be cases when normal and 
emergency ratings are legitimately equal, but that should only be true 
for a very small number of transmission lines.\614\ The SPP MMU notes 
that nearly 60% of transmission lines in SPP have identical normal and 
emergency ratings and argues that emergency ratings should only rarely 
be equal to normal ratings. Potomac Economics states that only roughly 
one third of the transmission line ratings provided for contingency 
constraints in MISO are emergency ratings compared to MISO's report 
that 90% of its binding constraints are contingent constraints that 
should be based on emergency ratings.\615\
---------------------------------------------------------------------------

    \614\ SPP MMU Comments at 4-5.
    \615\ Potomac Economics Comments at 7, 11.
---------------------------------------------------------------------------

    276. OMS contends that emergency ratings should serve as the 
foundation for AARs.\616\ OMS agrees with MISO Transmission Owners that 
normal and emergency ratings should not always be unique, but argues 
that transmission line ratings that are the same value can be derived 
using different methodologies.\617\ OMS contends that transmission 
owners have the responsibility to judge the reasonableness of using 
non-unique emergency ratings subject to transmission provider and 
market monitor review.\618\ EPRI states that high operating 
temperatures, other limiting elements in the circuit, and inability to 
withstand additional annealing (loss of tensile strength of the 
conductor through heating) may all contribute to finding emergency 
ratings that are identical to normal ratings, although such ratings 
would nonetheless be considered unique if they were developed using 
appropriate technical inputs.\619\ Many commenters express support for 
requirements to provide justifications when normal and emergency 
ratings are identical, given that it may be appropriate in some 
situations for normal and emergency ratings to be identical.\620\ TAPS 
states that the result of any individual transmission owner decision 
not to provide accurate emergency ratings may tie the hands of RTOs/
ISOs dealing with contingencies.\621\
---------------------------------------------------------------------------

    \616\ OMS Reply Comments at 11-12.
    \617\ Id. at 12.
    \618\ OMS Comments at 15.
    \619\ EPRI Comments at 7, 9-10.
    \620\ R Street Institute Comments at 3, 5; ACPA/SEIA Comments at 
16-17; EDFR Comments at 6; TAPS Comments at 2.
    \621\ TAPS Comments at 18.
---------------------------------------------------------------------------

    277. Transmission owners indicate that they use different durations 
for calculating emergency ratings, including hourly, daily, and two-day 
ahead short-term emergency ratings by Entergy,\622\ up to 30 minutes 
during post-contingency operations by APS,\623\ 30 minutes by 
PacifiCorp,\624\ and four hours by PG&E.\625\ Exelon states that it 
calculates four-hour emergency ratings, with long-term emergency and 
short-term emergency ratings set equal unless a shorter duration 
transmission line rating is feasible on the facility, as well as load 
dump ratings for up to 15 minutes.\626\ Exelon notes that flexibility 
in the duration of emergency ratings can be beneficial and some 
equipment, such as phase angle regulators, can allow the transmission 
owner to control the flow and avoid damage from shorter-term 
ratings.\627\ R Street Institute notes that some transmission operators 
use a 30 minute duration and others use two to four hour 
durations.\628\ OMS argues that emergency ratings must accurately 
reflect the capability of the transmission element for a standardized, 
limited period of time.\629\ OMS also contends that the Commission 
should require transmission providers to define what constitutes an 
emergency rating in their region and how they should be used.\630\
---------------------------------------------------------------------------

    \622\ Entergy Comments at 4.
    \623\ APS Comments at 7.
    \624\ PacifiCorp Comments at 4.
    \625\ PG&E Comments at 12.
    \626\ Exelon Comments at 21.
    \627\ Id. at 20.
    \628\ R Street Institute Comments at 7.
    \629\ OMS Comments at 13-14.
    \630\ Id. at 15.
---------------------------------------------------------------------------

    278. RTOs/ISOs similarly indicate that they use different durations 
for calculating emergency ratings, including long time emergency (four 
hours for winter, 12 hours for summer), short time emergency (15 
minutes), and drastic action limits (five minutes) in ISO-NE,\631\ up 
to four hours in CAISO (with some transmission owners providing shorter 
duration transmission line ratings),\632\ and 30 minutes in MISO.\633\ 
The SPP MMU recommends that emergency ratings be applicable on a 
shorter-term basis, meaning less than four hours in SPP, to observe 
limits of the equipment and prevent degradation.\634\ The SPP MMU does 
not recommend requiring transmission owners to exceed normal ratings to 
address challenges during sustained periods of contingencies or long 
duration events, such as polar vortex conditions.\635\ Potomac 
Economics recommends that any emergency ratings requirements specify 
the maximum permissible duration to enhance RTOs/ISOs' situational 
awareness and reliability.\636\
---------------------------------------------------------------------------

    \631\ ISO-NE Comments at 6.
    \632\ CAISO Comments at 1, 3.
    \633\ MISO Comments at 23.
    \634\ SPP MMU Comments at 13-14.
    \635\ Id. at 5.
    \636\ Potomac Economics Comments at 13.
---------------------------------------------------------------------------

    279. Many transmission owners express concern that the use of 
emergency ratings could risk degrading the asset and reducing its 
useful life.\637\ SDG&E states that it does not issue unique emergency 
ratings for certain types of equipment due to the potential for 
permanent damage.\638\ A few transmission owners note that the age and 
condition of the facilities impact whether an emergency rating may risk 
further damage to transmission equipment.\639\ Indicated PJM 
Transmission Owners state that for some facilities, even minimal use of 
emergency ratings can have a significant impact on the facility's 
useful life.\640\ Indicated PJM Transmission Owners note that the 
overuse of emergency ratings could cause asset degradation and in turn 
increase costs to consumers as those facilities have to be upgraded or 
replaced, while also having a negative impact on system 
reliability.\641\ Both NRECA/LPPC and Entergy note that if conductors 
violate sag requirements from the use of emergency ratings then they 
pose a risk to public

[[Page 2288]]

safety and reliability.\642\ Entergy lists several risks from the use 
of emergency ratings, including creep, elongation, and loss of 
conductor strength as well as the fact that several factors that 
determine emergency ratings cannot be known in advance, such as pre-
load current, pre-load temperature, contingency current, and 
theoretical contingency steady state temperature.\643\ According to 
EPRI, there are conditions when emergency ratings cannot be safely 
used, including when other parts of the circuit are already overloaded 
or when the conductor would be compromised or is too old.\644\ Entergy 
states that emergency ratings are risker than, and have a significantly 
greater potential to damage transmission equipment than, the use of 
AARs; therefore, Entergy contends, emergency ratings should be used for 
a short-term basis, on a limited number of facilities, and carefully 
monitored.\645\ Exelon states that emergency ratings are acceptable for 
a short duration, but warns that regular excessive loading will impact 
a facility's useful life.\646\
---------------------------------------------------------------------------

    \637\ See, e.g., APS Comments at 7; Dominion Comments at 4; EEI 
Comments at 17; Entergy Comments at 2; Exelon Comments at 22-23; 
Indicated PJM Transmission Owners Comments at 16-17; ITC Comments at 
12.
    \638\ SDG&E Comments at 4.
    \639\ EEI Comments at 17; Exelon Comments at 20.
    \640\ Indicated PJM Transmission Owners Comments at 17.
    \641\ Id. at 2-3; Entergy Comments at 15.
    \642\ NRECA/LPPC Comments at 25; Entergy Comments at 13.
    \643\ Entergy Comments at 13-14.
    \644\ EPRI Comments at 7.
    \645\ Entergy Comments at 11.
    \646\ Exelon Comments at 22-23.
---------------------------------------------------------------------------

    280. NRECA/LPPC argues that emergency ratings may not be 
applicable, beneficial, or sustainable for all transmission lines.\647\ 
Indicated PJM Transmission Owners note that there is a balance between 
the benefits of emergency ratings and the negative impacts of overuse 
or misuse of emergency ratings.\648\ Indicated PJM Transmission Owners 
claim that the use of emergency ratings may reduce costs to consumers 
in some short-term cases but there is no evidence to support savings in 
the long term and instead their use will likely increase transmission 
costs.\649\ PacifiCorp asserts that implementing requirements for 
emergency ratings on equipment other than transmission lines would 
require voluminous amounts of data and additional databases and 
personnel.\650\ EEI states that universal use of seasonal and emergency 
ratings may provide only a negligible improvement beyond current 
transmission line ratings.\651\ BPA asserts that it currently operates 
to its maximum operating temperature limits, and therefore would see no 
increase in capacity from the use of emergency ratings.\652\ Dominion 
states that it does not use emergency ratings for ATC calculations on 
the Dominion Energy South Carolina system because emergency ratings are 
for short durations and specific circumstances.\653\
---------------------------------------------------------------------------

    \647\ NRECA/LPPC Comments at 25.
    \648\ Indicated PJM Transmission Owners Comments at 3.
    \649\ Id. at 15-17.
    \650\ PacifiCorp Comments at 5.
    \651\ EEI Comments at 4.
    \652\ BPA Comments at 7.
    \653\ Dominion Comments at 13.
---------------------------------------------------------------------------

    281. On the other hand, PacifiCorp states that it has seen no 
detriment to reliability from using emergency ratings for their 
transmission lines for over a decade.\654\ WAPA states that using 
emergency ratings for short durations does not pose too much risk to 
the integrity and condition of the device.\655\
---------------------------------------------------------------------------

    \654\ PacifiCorp Comments at 4.
    \655\ WAPA Comments at 8.
---------------------------------------------------------------------------

    282. Several commenters note methods to manage the impact of 
emergency ratings on equipment. MISO recommends that the Commission 
allow transmission owners to establish reasonable and supported 
reliability margins where higher emergency ratings are established such 
as: (1) A safety margin to ensure the transmission line rating is less 
than the relay trip rating and maximum power transfer rating; and (2) 
allowing defined, reasonable limits on the duration and frequency of 
emergency ratings.\656\ Potomac Economics argues that emergency ratings 
are designed to permit temporary use without equipment damage, such as 
significant annealing, and states that if post-contingent responses are 
in question, RTOs/ISOs can and do develop special operating guides to 
specify the operating conditions required to use emergency ratings and 
maintain reliability.\657\ Potomac Economics contends that transmission 
owners should continue to have the authority and responsibility to 
determine reliable emergency ratings, but states that vague or general 
concerns should not forestall requirements to provide emergency ratings 
for most facilities.\658\ Tangibl also notes that sag limitations can 
be addressed in some cases.\659\
---------------------------------------------------------------------------

    \656\ MISO Comments at 26.
    \657\ Potomac Economics Comments at 14.
    \658\ Id. at 14.
    \659\ Tangibl Comments at 5.
---------------------------------------------------------------------------

    283. Several commenters identify benefits of emergency ratings use, 
including increased transfer capability and relieving congestion, which 
can be a valuable reliability tool \660\ and also lead to lower prices 
for customers.\661\ Several other commenters point to more efficient 
use of the transmission system as a result of emergency ratings.\662\ 
Potomac Economics' analysis, for example, found the potential for $48.1 
million in 2019 and $49.5 million in 2020 in savings in MISO alone that 
could have been realized by using emergency ratings for facilities for 
which only normal ratings were provided.\663\
---------------------------------------------------------------------------

    \660\ EDFR Comments at 6.
    \661\ ISO-NE Comments at 10; New England State Agencies Comments 
at 21; PacifiCorp Comments at 4; Potomac Economics Comments at 8, 
10; WAPA Comments at 8.
    \662\ Tangibl Comments at 5; EDFR Comments at 6; ACP Comments at 
16-17.
    \663\ Potomac Economics Comments at 8.
---------------------------------------------------------------------------

    284. Indicated PJM Transmission Owners express concern with Potomac 
Economics' emergency rating cost and benefit analysis, though, noting 
the absence of increased operations, maintenance, and capital costs 
associated with running the system at emergency conditions.\664\ MISO 
Transmission Owners similarly express concern with Potomac Economics' 
analysis and state that the Commission should not rely on that 
analysis, including estimates that the lack of unique emergency ratings 
by some transmission owners in MISO contributed to $62-68 million in 
extra congestion costs.\665\
---------------------------------------------------------------------------

    \664\ Indicated PJM Transmission Owners Comments at 16.
    \665\ MISO Transmission Owners Comments at 43-44.
---------------------------------------------------------------------------

    285. In its reply comments, Potomac Economics contends that their 
estimations are conservative and emphasize the importance of using 
emergency ratings, since the cost savings are comparable to the 
benefits of AARs.\666\ Potomac Economics also notes that requirements 
to implement emergency ratings would still be placed on transmission 
owners, and they retain discretion in setting emergency ratings based 
on reliability, subject to transparency and their reasonableness.\667\ 
The SPP MMU states that accurate emergency ratings would make 
transmission congestion more uniformly defined throughout the 
footprint, thus helping reduce congestion and creating more uniform 
prices.\668\ Potomac Economics argues that emergency ratings provide 
additional benefits beyond more efficient use of the transmission 
system and enhanced reliability, including increased operational 
awareness for RTOs/ISOs and other transmission providers regarding the 
capability of the transmission facilities.\669\ New England State 
Agencies argue that accurate emergency ratings could prevent 
unnecessary curtailment of generation, and in extreme circumstances, 
avoid

[[Page 2289]]

shedding load.\670\ R Street Institute similarly contends that the 
benefits of emergency ratings go beyond the production cost savings 
estimated by Potomac Economics and include avoided customer 
outages.\671\ R Street Institute notes that the cost of additional wear 
must consider the frequency and duration of emergency rating use, which 
is usually uncommon and brief.\672\ EPRI contends that emergency 
ratings will provide less benefits when AARs or DLRs are already used 
because the starting temperature of the conductor may be higher than 
under static ratings.\673\
---------------------------------------------------------------------------

    \666\ Potomac Economics Reply Comments at 6-7.
    \667\ Id. at 11.
    \668\ SPP MMU Comments at 13.
    \669\ Potomac Economics Comments at 8, 10.
    \670\ New England State Agencies Comments at 21.
    \671\ R Street Institute Comments at 8.
    \672\ Id. at 8.
    \673\ EPRI Comments at 8.
---------------------------------------------------------------------------

    286. ACPA/SEIA state that emergency ratings are important to ensure 
safe operating conditions and because they often determine the loading 
allowed on constrained facilities even during normal conditions.\674\ 
Tangibl also contends that unique emergency ratings may reveal 
potential low-cost system upgrades, allow more efficient transmission 
planning, reduce the time and cost of interconnection studies, and 
reduce barriers to the development of new generation.\675\ 
Additionally, Tangibl notes that when unique emergency ratings are not 
used, it potentially causes needless curtailments for renewable energy 
projects.\676\ R Street Institute contends that emergency ratings 
should be required regardless of RTO/ISO participation, to avoid a 
disincentive to RTO/ISO membership, and that inaccurate emergency 
ratings are unjust and unreasonable.\677\ R Street Institute recognizes 
that the record on emergency ratings is sparse and that implementing 
emergency ratings may be prone to operator error, but notes that they 
are sometimes used implicitly during emergency conditions.\678\
---------------------------------------------------------------------------

    \674\ ACPA/SEIA Comments at 16-17.
    \675\ Tangibl Comments at 4-6.
    \676\ Id. at 5-6.
    \677\ R Street Institute Comments at 5-7.
    \678\ Id. at 3, 7.
---------------------------------------------------------------------------

    287. Almost all transmission owners that discussed emergency 
ratings in their comments agree that emergency ratings should be used 
judiciously for reliability reasons, and not regularly for economics, 
to access additional transfer capability.\679\ Entergy states that 
emergency ratings can be used only in real-time operations and should 
not be used in markets.\680\ Indicated PJM Transmission Owners agree 
with the NOPR statement that emergency ratings allow for higher 
operating limits, and thus, more efficient system commitment and 
dispatch solutions, but argues that emergency ratings should be used 
only during emergencies and not to increase capacity during normal 
operating conditions due to the risks of wear and additional 
costs.\681\ Dominion and EEI advocate for using emergency ratings only 
on an as-needed basis.\682\ Exelon contends that the benefits of using 
emergency ratings under emergency conditions outweigh the costs.\683\
---------------------------------------------------------------------------

    \679\ See, e.g., Dominion Comments at 13; Entergy Comments at 2; 
Exelon Comments at 22; Indicated PJM Transmission Owners Comments at 
17.
    \680\ Entergy Comments at 2.
    \681\ Indicated PJM Transmission Owners Comments at 15-16.
    \682\ Dominion Comments at 13; EEI Comments at 16-17.
    \683\ Exelon Comments at 22.
---------------------------------------------------------------------------

    288. Potomac Economics argues that the Commission should clarify 
that the unique emergency ratings be applied for contingent 
constraints, stating that approximately half of the potential benefits 
and reduced production costs of the rulemaking could be lost without 
such a clarification.\684\ New England State Agencies and OMS agree 
that accurate emergency ratings could provide important benefits.\685\ 
However, New England State Agencies argue that more information is 
needed.\686\
---------------------------------------------------------------------------

    \684\ Potomac Economics Comments at 4.
    \685\ New England State Agencies Comments at 21; OMS Comments at 
13-14.
    \686\ New England State Agencies Comments at 22.
---------------------------------------------------------------------------

    289. Regarding implementation, PacifiCorp states that the ability 
to use emergency ratings in TTC on path ratings \687\ is more complex 
than being able to calculate them because this requires contingency 
analysis.\688\ Entergy states that emergency ratings implementation is 
complicated by the thermal time constraint being different for all 
conductors based on size and construction.\689\
---------------------------------------------------------------------------

    \687\ The NERC Glossary defines ``Rated System Path 
Methodology,'' which includes an initial TTC from which the ATC is 
derived and is generally reported as specific transmission path 
capabilities. NERC, Glossary of Terms Used in NERC Reliability 
Standards (June 28, 2021), https://www.nerc.com/pa/Stand/Glossary%20of%20Terms/Glossary_of_Terms.pdf.
    \688\ PacifiCorp Comments at 5.
    \689\ Entergy Comments at 13-14.
---------------------------------------------------------------------------

    290. ITC asserts that AARs should be used for both normal ratings 
(pre-contingency operations) and emergency ratings (post-contingency 
operations) because congestion is often caused by projected post-
contingency flows.\690\ EDFR and Industrial Customer Organizations 
state that, where appropriate, emergency ratings could be combined with 
DLRs for additional benefits.\691\ Similarly, PG&E supports considering 
the benefits of AARs for both normal and emergency ratings.\692\ By 
contrast, ACPA/SEIA encourage the consideration of seasonal line rating 
information in developing emergency ratings, similar to the framework 
for using seasonal line ratings for long-term transmission 
service.\693\
---------------------------------------------------------------------------

    \690\ ITC Comments at 12.
    \691\ EDFR Comments at 6; Industrial Customer Organizations 
Comments at 27.
    \692\ PG&E Comments at 12.
    \693\ ACPA/SEIA Comments at 17.
---------------------------------------------------------------------------

    291. ISO-NE states that an update to the overall transmission line 
rating methodology to include AARs may also necessitate the need for 
new emergency ratings based on those AARs.\694\ Potomac Economics 
supports a requirement that transmission owners calculate and use AARs 
based on emergency ratings for contingency constraints.\695\ NYTOs 
state that having normal and emergency ratings could preempt the need 
to establish an AAR mandate on all transmission lines.\696\
---------------------------------------------------------------------------

    \694\ ISO-NE Comments at 10-11.
    \695\ Potomac Economics Reply Comments at 8.
    \696\ NYTOs Comments at 11.
---------------------------------------------------------------------------

b. Commission Determination
    292. Based on the record developed in this proceeding, we are 
persuaded that it is appropriate to adopt certain requirements for 
emergency ratings. Whether and how a transmission owner establishes 
emergency ratings is important because emergency ratings are a critical 
input into determining transfer capability, both during normal 
operations and during post-contingency operations. There is a 
significant record of transmission owners and transmission providers 
already using emergency ratings.\697\ For example, Exelon notes that it 
already calculates emergency ratings for its transmission facilities 
and that the benefits of using emergency ratings during emergencies 
outweigh the costs of establishing them.\698\ There is also an 
extensive record on the role of emergency ratings in ensuring reliable 
and efficient operations. Specifically, transmission owners and 
transmission providers report benefits from implementing emergency 
ratings including increased transmission capacity,\699\ additional time 
to respond to contingencies,\700\ lower costs to consumers,\701\ and 
help

[[Page 2290]]

maintaining reliability and avoiding unnecessary load shed.\702\ 
Emergency ratings have an extensive record of use and are a more 
accurate representation of the flow limits over shorter timeframes and 
are thus necessary to ensure just and reasonable wholesale rates.
---------------------------------------------------------------------------

    \697\ See, e.g., APS Comments at 7; Dominion Comments at 4; 
Entergy Comments at 1; EEI Comments at 16; Exelon Comments at 22; 
Indicated PJM Transmission Owners Comments at 2; PacifiCorp Comments 
at 4; PG&E Comments at 12; SDG&E Comments at 3; WAPA Comments at 8.
    \698\ Exelon Comments at 22.
    \699\ ISO-NE Comments at 10; PacifiCorp Comments at 4.
    \700\ APS Comments at 7.
    \701\ ISO-NE Comments at 10; PacifiCorp Comments at 4; WAPA 
Comments at 8.
    \702\ Exelon Comments at 22.
---------------------------------------------------------------------------

    293. First, as set forth under ``Obligations of Transmission 
Provider'' in pro forma OATT Attachment M, we require that transmission 
providers use emergency ratings for contingency analysis in the 
operations horizon and in post-contingency simulations of constraints. 
We define an ``emergency rating'' in pro forma OATT Attachment M as a 
transmission line rating that reflects operation for a specified, 
finite period, rather than reflecting continuous operation. An 
emergency rating may assume acceptable loss of equipment life or other 
physical or safety limitations for the equipment involved.\703\ We 
adopt this emergency ratings requirement to ensure the accuracy of 
transmission line ratings, particularly during emergency operations. 
Emergency ratings are a critical input into determining transfer 
capabilities and congestion costs during emergency operations and can 
provide temporarily expanded operating flexibility to allow higher 
loading and higher operating limits on transmission facilities for a 
short time during unexpected tight system conditions, emergency events, 
or contingencies. Emergency ratings are also a critical input into the 
scheduling of transactions that can be executed under real-time 
operating constraints. Because real-time, unforeseen contingencies can 
occur that stress the system's transfer capabilities (e.g., forced 
outages on generation or transmission), transmission providers operate 
their systems in normal conditions to be able to withstand such 
contingencies. Should such a contingency occur, transmission providers 
are thus prepared to redispatch resources. Dispatching and scheduling 
resources to accommodate such contingency events can cause a large 
increase in wholesale rates, due to congestion costs. More accurate 
emergency ratings (like more accurate transmission line ratings 
generally) will better reflect the near-term transfer capability of the 
system, more accurately reflect the cost of serving load, and avoid 
unnecessary transient congestion costs. For these reasons, we adopt the 
emergency ratings requirement as set forth in pro forma OATT Attachment 
M.
---------------------------------------------------------------------------

    \703\ The NERC Glossary defines an ``Emergency Rating'' as: 
``[t]he rating as defined by the equipment owner that specifies the 
level of electrical loading or output, usually expressed in 
megawatts (MW) or Mvar or other appropriate units, that a system, 
facility, or element can support, produce, or withstand for a finite 
period. The rating assumes acceptable loss of equipment life or 
other physical or safety limitations for the equipment involved.'' 
NERC, Glossary of Terms Used in NERC Reliability Standards (June 28, 
2021), https://www.nerc.com/pa/Stand/Glossary%20of%20Terms/Glossary_of_Terms.pdf.
---------------------------------------------------------------------------

    294. Second, we require that transmission providers use uniquely 
determined emergency ratings. Under this requirement, transmission 
providers must use emergency ratings that transmission owners determine 
uniquely from their determination of normal ratings.\704\ This 
requirement ensures that transmission providers use emergency ratings 
that reflect that a transmission facility's transfer capabilities may 
differ for shorter periods of time; that is, transfer capabilities 
differ if calculated for use over a short period of time (i.e., for 
emergency ratings) rather than for use over an indefinite period of 
time (i.e., for normal ratings).
---------------------------------------------------------------------------

    \704\ As clarified below, consistent with our determination in 
Section IV.B.2.b.iii. on the role of the transmission owner and 
transmission provider in AAR implementation, transmission owners, 
not transmission providers, are responsible for calculating 
emergency ratings.
---------------------------------------------------------------------------

    295. In response to commenters stating that the Commission should 
not require that emergency ratings be unique from normal ratings, we 
clarify that we are not requiring that emergency ratings be arbitrarily 
higher than normal ratings. Instead, we are requiring that emergency 
ratings be uniquely determined, meaning determined based on assumptions 
that reflect the specified, finite duration of emergency ratings, as 
distinct from the assumptions used to calculate normal ratings, which 
reflect a power transfer capability that can be maintained 
indefinitely. Consistent with the Commission's statements in the 
NOPR,\705\ transmission owners will have discretion to determine the 
procedure used to calculate emergency ratings, so long as they do so in 
accordance with good utility practice and the other requirements in pro 
forma OATT Attachment M. Accordingly, a transmission provider may use 
an emergency rating equal to a normal rating, provided that both 
ratings were calculated uniquely using appropriate assumptions, sound 
engineering judgment, and good utility practice.
---------------------------------------------------------------------------

    \705\ NOPR, 173 FERC ] 61,165 at P 46 n.57.
---------------------------------------------------------------------------

    296. We agree with PacifiCorp's comment that the ability to use 
uniquely determined emergency ratings requires real-time and near real-
time horizons contingency analysis tools that can handle variable 
limits (i.e., normal rating for normal operating conditions, and 
emergency ratings in contingency conditions) and perform iterative 
simulations to calculate TTC on path ratings.\706\ Such contingency 
analysis is already required under NERC Reliability Standards, 
including, e.g., Reliability Standards TOP-001 and IRO-008, which 
require transmission providers and reliability coordinators to perform 
a real-time assessment at least once every 30 minutes to ensure that 
instability, uncontrolled separation, or cascading outages that could 
adversely impact the reliability of the interconnection will not 
occur.\707\ Modifications to future-looking cases to increase flow, and 
to iteratively run contingency analysis, is common practice since 
system loading conditions change throughout the day. However, we agree 
that these tools require additional data points and simulation process 
modifications to observe the emergency rating of bulk electric system 
facilities, if not currently used.
---------------------------------------------------------------------------

    \706\ PacifiCorp Comments at 5-6.
    \707\ Reliability Standard TOP-001-5 R13 requires a transmission 
operator to perform a Real-Time Assessment at least once every 30 
minutes. According to the NERC Glossary, a ``Real-Time Assessment'' 
is: ``[a]n evaluation of system conditions using Real-time data to 
assess existing (pre-Contingency) and potential (post-Contingency) 
operating conditions. The assessment shall reflect applicable inputs 
including, but not limited to: . . . Facility Ratings; and 
identified phase angle and equipment limitations.'' NERC, Glossary 
of Terms Used in NERC Reliability Standards (June 28, 2021), https://www.nerc.com/pa/Stand/Glossary%20of%20Terms/Glossary_of_Terms.pdf.
---------------------------------------------------------------------------

    297. Third, we require that emergency ratings also incorporate an 
adjustment for ambient air temperature and for daytime/nighttime solar 
heating, consistent with the AAR requirements for normal ratings. Based 
on the record, we find that the calculation of AARs for both normal and 
emergency ratings will enhance the accuracy of transmission line 
ratings and ensure just and reasonable wholesale rates. As commenters 
point out, congestion is often caused by post-contingency transmission 
flows that are modeled and managed as part of normal operations, and 
thus not requiring AARs to be applied to emergency ratings would 
inaccurately constrain even normal operations and prevent significant 
potential benefits of AAR implementation. Finally, we note that 
applying AARs to emergency ratings is consistent with the 
implementation of AARs in PJM, where nearly all emergency ratings are 
dependent on ambient air temperatures.\708\
---------------------------------------------------------------------------

    \708\ See PJM Ratings Information, https://www.pjm.com/markets-and-operations/etools/oasis/system-information/ratings-information.aspx (last visited Nov. 1, 2021).

---------------------------------------------------------------------------

[[Page 2291]]

    298. As with the application of AARs to normal ratings, 
transmission owners have discretion to determine which specific 
electric system equipment has emergency ratings that are affected by 
ambient air temperatures, consistent with good utility practice and the 
requirements of pro forma OATT Attachment M.
    299. Consistent with our determination in Section IV.B.2.b.iii on 
the role of the transmission owner and transmission provider in AAR 
implementation, we clarify that transmission owners, not transmission 
providers, are responsible for calculating emergency ratings. This 
responsibility is set forth in the NERC Reliability Standards, as well 
as in RTO/ISO foundational documents.\709\ Nothing in this final rule 
changes that responsibility. In the non-RTO/ISO regions, this is 
generally not a concern because the transmission provider is usually 
the transmission owner. However, in the RTO/ISO regions, there is a 
distinction between transmission owners and transmission providers. 
Thus, in order to comply with this final rule, RTOs/ISOs--the 
transmission provider with the OATT on file--will need to rely on their 
member transmission owners to calculate emergency ratings and provide 
them to the RTO/ISO.\710\ Additionally, unlike normal transmission line 
ratings, emergency ratings correspond to a specific duration. Thus, the 
duration of each uniquely determined emergency rating determined by a 
transmission owner must be specified and communicated by the 
transmission provider, consistent with our determination on the 
transparency and reporting requirements of transmission line ratings in 
Section IV.G.3 below.
---------------------------------------------------------------------------

    \709\ See, e.g., Reliability Standards FAC-008-5, Requirement R3 
and FAC-008-5, Requirement R6.
    \710\ See supra note 326.
---------------------------------------------------------------------------

    300. Where the transmission provider is not the transmission owner 
(e.g., RTOs/ISOs), we require the transmission provider to explain in 
its compliance filing, as part of its implementation of new pro forma 
OATT Attachment M, through what mechanism (tariff, membership 
agreement, etc.) the transmission owner has the obligation for making 
and communicating to the transmission provider the timely calculations 
and determinations related to emergency ratings (including any 
discretion in calculations).
    301. In response to commenter requests for a minimum, maximum, or 
standardized emergency rating duration, we recognize that transmission 
owners use a range of durations and find that transmission owners are 
best situated to make judgments on the appropriate emergency rating 
duration based on the technical capabilities of the installed 
equipment, consistent with good utility practice, using sound 
engineering judgment, manufacturer guidance, and equipment reliability 
experience.
    302. We recognize, as pointed out by some commenters, that 
emergency ratings can affect the safe operation and useful life of 
transmission facilities. However, as several commenters explain, most 
transmission equipment has the ability to withstand high currents for 
short periods of time without sustaining damage.\711\ The requirement 
to implement uniquely determined emergency ratings simply requires that 
emergency ratings calculations be based on this existing ability, where 
it exists. In response to comments from MISO that the Commission allow 
transmission owners to establish reasonable and supported reliability 
margins,\712\ as the Commission stated in the NOPR, transmission 
providers that find they need a reliability margin have existing 
Commission-approved mechanisms, such as the transmission reliability 
margin component of ATC, for establishing such a margin on a consistent 
and transparent basis.\713\
---------------------------------------------------------------------------

    \711\ See, e.g., Entergy Comments at 6-8; BPA Comments at 7; 
Exelon Comments at 21-23.
    \712\ MISO Comments at 26.
    \713\ NOPR, 173 FERC ] 61,165 at P 104.
---------------------------------------------------------------------------

    303. In response to Indicated PJM Transmission Owners and MISO 
Transmission Owners' concerns with Potomac Economics' analysis, we note 
that our findings in this final rule are not solely based on Potomac 
Economics' analysis. Rather, our rationale for adopting the requirement 
to implement uniquely determined emergency ratings, similar to the AAR 
requirements discussed above, is based on the finding that implementing 
uniquely determined emergency ratings will ensure that transmission 
line ratings are more accurate, that more accurate transmission line 
ratings will ensure wholesale rates more accurately reflect the cost of 
the wholesale service being provided, and, thus, that those wholesale 
rates are just and reasonable.
3. Equipment for Which Emergency Ratings Must Be Calculated
a. Comments
    304. Exelon and APS note that they can and do calculate emergency 
ratings on equipment other than conductors and transformers.\714\ APS 
notes that its use of emergency ratings often does not impact, and 
typically is not limited by, substation equipment.\715\ Entergy states 
that emergency ratings cannot be used on many components of 
facilities.\716\ However, Entergy explains that autotransformers can 
have emergency ratings about 25 to 30% over their normal rating for up 
to two hours.\717\ Tangibl notes that different equipment may be 
limiting under different operating scenarios and that, while secondary 
and control components often have identical normal and emergency 
ratings, it is rare for relays to be the limiting element in PJM winter 
ratings.\718\
---------------------------------------------------------------------------

    \714\ APS Comments at 7; Exelon Comments at 21.
    \715\ APS Comments at 7.
    \716\ Entergy Comments at 7.
    \717\ Id. at 7.
    \718\ Tangibl Comments at 3.
---------------------------------------------------------------------------

b. Commission Determination
    305. As we determined in Section IV.A above, emergency ratings, 
like all transmission line ratings, must incorporate a set of 
electrical equipment ratings that collectively operate as a single 
electric system element (e.g., transformers, relay protective devices, 
terminal equipment, and series and shunt compensation devices), and the 
most limiting component from that set will determine the transmission 
line rating. Consistent with our determination on the use of AARs in 
Section IV.B.1 above, we find that transmission providers must use 
uniquely determined emergency ratings on all conductors and all 
relevant transmission equipment, in order to ensure that transmission 
line ratings are accurate.

G. Transparency

1. NOPR Proposal
    306. The Commission proposed in the NOPR to require transmission 
owners to share transmission line ratings for each period for which 
they are calculated and transmission line rating methodologies with 
their transmission provider(s), and, in regions served by an RTO/ISO, 
also with the market monitor(s) of that RTO/ISO.\719\ The Commission 
preliminarily found that this requirement would afford transmission 
providers and market monitors more operational and situational 
awareness.\720\
---------------------------------------------------------------------------

    \719\ NOPR, 173 FERC ] 61,165 at P 125.
    \720\ Id. P 126.
---------------------------------------------------------------------------

    307. The Commission also acknowledged that sharing transmission 
line ratings and transmission line rating methodologies with other, 
additional, interested parties would allow for

[[Page 2292]]

greater transparency and, in the case of transmission providers, may 
aid efforts to manage congestion along mutual seams and may be 
beneficial for the study of affected systems during the interconnection 
process.\721\ The Commission thus sought comment on whether to require 
transmission owners to share, upon request, their transmission line 
ratings and transmission line rating methodologies with transmission 
providers other than the transmission owner's own transmission 
provider. The Commission also sought comment on whether to require 
transmission owners to make their transmission line ratings and 
transmission line rating methodologies available to other interested 
stakeholders, including by posting information on their OASIS page or 
other password-protected online forums.\722\
---------------------------------------------------------------------------

    \721\ Id. P 129.
    \722\ Id.
---------------------------------------------------------------------------

    308. While the Commission did not propose new auditing requirements 
in the NOPR, the Commission reiterated that it would continue to 
conduct reviews of transmission line ratings as a component of broader 
tariff compliance audits.\723\
---------------------------------------------------------------------------

    \723\ Id. P 130.
---------------------------------------------------------------------------

2. Comments
a. Increased Transparency Requirements for Transmission Line Ratings 
Methodologies
    309. Many commenters express general support for the Commission's 
efforts to increase transparency surrounding transmission line ratings 
and methodologies.\724\ MISO Transmission Owners argue that the 
transparency proposal in the NOPR seems reasonable, but should not be 
broadened, explaining that the transparency proposal in the NOPR 
balances the need for transparency for RTOs/ISOs and market monitors 
with the need for confidentiality.\725\ Industrial Customer 
Organizations state that transparency is a prerequisite for 
stakeholders to independently evaluate the potential reliability 
benefits of more accurate transmission line ratings, for the Commission 
to ensure just and reasonable rates, to reduce the incentives and 
opportunities for transmission owners to understate or manipulate 
transmission line ratings, and for transmission providers to identify 
cost-effective congestion management solutions.\726\ EDFR claims that 
increased transparency may result in more efficient and standardized 
transmission line rating methodologies while identifying outliers more 
quickly and that transparency encourages the use of a balanced, 
reasonable transmission line rating methodology, which should result in 
more accurate transmission line ratings.\727\ OMS states that the 
Commission's regulations require transmission line rating 
transparency.\728\ OMS further contends that transparency should be the 
default position and should only be restricted where demonstrably 
necessary.\729\ EPSA states that transparent collection and disclosure 
of quality data is the lynchpin of an efficient transmission 
system.\730\ Certain TDUs state that improved transparency of 
transmission line ratings processes will ultimately lead to a more 
efficient and cost-effective grid.\731\ IID supports the Commission's 
proposed requirements and encourages the Commission to consider how 
such information can be shared in a timely manner, such that adjacent 
operators and users of the grid can account for current transmission 
line ratings in their weekly and day-ahead planning.\732\
---------------------------------------------------------------------------

    \724\ MISO Transmission Owners Comments at 19; Entergy Comments 
at 16; NRECA/LPPC Comments at 27-28; AEP Comments at 5; DC Energy 
Comments at 5; IID Comments at 7.
    \725\ MISO Transmission Owners Comments at 36.
    \726\ Industrial Customer Organizations Comments at 28-29.
    \727\ EDFR Comments at 7.
    \728\ OMS Comments at 17 n.57 (citing 18 CFR 37.6).
    \729\ OMS Reply Comments at 3-4.
    \730\ EPSA Comments at 3.
    \731\ Certain TDUs Comments 8.
    \732\ IID Comments at 7.
---------------------------------------------------------------------------

b. Sharing Transmission Line Ratings and Methodologies With 
Transmission Providers and Market Monitors
    310. Nearly all commenters support the proposal in the NOPR to 
require transmission owners to share transmission line ratings and 
methodologies with the relevant transmission provider and, in the case 
of transmission providers that are RTOs/ISOs, the relevant market 
monitor.\733\ AEP and Exelon note that PJM posts actual transmission 
line ratings publicly.\734\
---------------------------------------------------------------------------

    \733\ AEP Comments at 8; CAISO DMM Comments at 3, 7-8; OMS 
Comments at 16; Exelon Comments at 23-24; DC Energy Comments at 5; 
Potomac Economics Comments at 16; IID Comments at 7; New England 
State Agencies Comments at 17-19; R Street Institute Comments at 3; 
SPP MMU Comments at 5; TAPS Comments at 23.
    \734\ AEP Comments at 8; Exelon Comments at 23-24.
---------------------------------------------------------------------------

    311. DC Energy contends that implementing AARs and DLRs and 
requiring RTOs/ISOs to post the transmission line ratings used for each 
constraint-binding interval for both the day-ahead and real-time 
markets is not an infeasible or unduly burdensome task.\735\ DC Energy 
notes that ERCOT publishes every transmission line rating used for 
every constraint's binding interval for both its day-ahead and real-
time markets on its market information system portal accessible by all 
market participants.\736\
---------------------------------------------------------------------------

    \735\ DC Energy Comments at 5.
    \736\ Id.
---------------------------------------------------------------------------

    312. Potomac Economics contends that the information shared must 
include the limiting element for each transmission line rating and the 
inputs necessary to replicate the transmission line rating calculation 
to monitor for transmission withholding, and that such information 
should be maintained in a database accessible by those with a role in 
monitoring, operating, and planning the transmission system.\737\ EDFR 
supports a requirement that transmission owners provide information 
identifying the transmission line's limiting element.\738\ New England 
State Agencies agree with the reforms proposed in the NOPR with a 
minimum of requiring disclosure of transmission line ratings and 
methodologies to all grid operators and market monitors.\739\ New 
England State Agencies state such a requirement would allow 
verification of the existing transmission line ratings by independent 
authorities.\740\ New England State Agencies assert that providing data 
to the RTO/ISO market monitor would allow the market monitor to verify 
the quality and accuracy of the information.\741\ New England State 
Agencies contend that transmission owners may have an incentive to be 
overly conservative with transmission line ratings methodologies 
because there is no financial incentive for more efficient operation of 
existing transmission assets and there is significant incentive for 
transmission owners to build new transmission lines and substations and 
include these new assets in their rate base.\742\ Because NYISO and PJM 
already require similar data disclosure, New England State Agencies 
claim that transmission owners can comply without undue difficulty with 
the proposed requirements and that there is no actual evidence in the 
record of any increased litigation in those regions where disclosure is 
common.\743\
---------------------------------------------------------------------------

    \737\ Potomac Economics Comments at 16-17.
    \738\ EDFR Comments at 6.
    \739\ New England State Agencies Comments at 19.
    \740\ Id.
    \741\ Id. at 17-18.
    \742\ Id. at 18.
    \743\ Id. at 20.
---------------------------------------------------------------------------

    313. NRECA/LPPC caution that their members do not believe the 
Commission

[[Page 2293]]

should require RTOs/ISOs to develop and maintain comprehensive 
databases to document the limiting element of all transmission circuits 
and facilities in their regions, arguing that the benefit to consumers 
is unclear and that the NOPR does not support such a requirement.\744\
---------------------------------------------------------------------------

    \744\ NRECA/LPPC Comments at 27-28.
---------------------------------------------------------------------------

    314. Only two commenters object to the proposed transparency 
requirements. Dominion states that requiring that transmission line 
ratings and methodologies be disclosed to the RTO/ISO market monitor is 
unwarranted because transmission line ratings are primarily reliability 
tools and are effectively overseen by NERC.\745\ Dominion states that 
it already provides transmission line ratings to PJM and PJM makes them 
publicly available.\746\ While Dominion does not object to continuing 
these practices, Dominion does object to providing its transmission 
line rating methodology to the PJM market monitor, which Dominion 
argues has no oversight over the operation of the PJM transmission 
system.\747\ Separately, ITC argues that requirements to make all 
transmission line ratings available to the RTOs/ISOs, market monitor, 
and other stakeholders would be unduly burdensome.\748\ ITC states that 
only a small number of transmission lines contribute to congestion and 
that regular reporting may increase the probability of inconsistencies 
between ITC's internal databases and those used for external data 
requests.\749\ ITC therefore requests that the final rule require 
transmission owners to provide such data only upon request. ITC argues 
that RTOs/ISOs and market monitors should use shared transmission line 
ratings for informational purposes only and not for standardization 
purposes.\750\
---------------------------------------------------------------------------

    \745\ Dominion Comments at 14-15.
    \746\ Id.
    \747\ Id.
    \748\ ITC Comments at 13.
    \749\ Id.
    \750\ Id.
---------------------------------------------------------------------------

c. Transmission Providers Sharing Transmission Line Ratings and 
Methodologies With Any Transmission Provider
    315. Several commenters support a requirement for transmission 
providers to share, upon request, transmission line ratings and 
methodologies with any transmission provider.\751\ APS states that this 
sharing of information is essential to ensure security in APS's 
transmission operator area.\752\ MISO states that, in addition to the 
proposed transparency requirements in the NOPR, sharing the same 
information with neighboring transmission providers that share a seam 
with MISO is needed.\753\ MISO asserts that such sharing of these 
transmission line ratings would be necessary for both tie lines and 
interregional congestion management, useful for reliability studies 
involving the neighboring regions, consistent with other coordination 
practices, and subject to confidentiality restrictions to control 
dissemination.\754\ Similarly, Vistra argues that the Commission should 
clarify that transmission providers must share AAR information with 
neighboring transmission providers because transmission line rating 
calculations typically consider loop flows.\755\ Vistra explains that, 
logistically, this information sharing could take many forms, including 
direct data pushes between transmission providers or publishing such 
information on OASIS sites and that the Commission need not dictate a 
particular information sharing method.\756\
---------------------------------------------------------------------------

    \751\ APS Comments at 8; PacifiCorp Comments at 3; MISO Comments 
at 29; EPSA Comments at 3; Exelon Comments at 27; IID Comments at 7.
    \752\ APS Comments at 8.
    \753\ MISO Comments at 29.
    \754\ Id.
    \755\ Vistra Comments at 7-8.
    \756\ Id.
---------------------------------------------------------------------------

d. Sharing Transmission Line Ratings and Methodologies With Other 
Entities
    316. Some commenters support requiring the sharing of transmission 
line ratings and methodologies with entities other than transmission 
providers and market monitors.\757\ For example, WATT contends that 
transmission line rating methodologies need to be shared with all 
transmission customers.\758\ R Street Institute argues that the NOPR 
proposal would provide insufficient transparency and that, ideally, 
transmission line ratings and methodologies would be available to a 
broader set of market participants and state commissions as well.\759\ 
OMS similarly asserts that all stakeholders should be able to see 
transmission line ratings and that the market monitor and MISO should 
be granted complete transparency into the methods used to create these 
transmission line ratings, recognizing that the regional entities are 
strictly focused on reliability.\760\
---------------------------------------------------------------------------

    \757\ APS Comments at 9; Clean Energy Parties Comments at 14; 
EPSA Comments at 3; Exelon Comments at 28-29; EDFR Comments at 7; 
New England State Agencies Comments at 20; OMS Comments at 16; R 
Street Institute Comments at 3; TAPS Comments at 24; WATT Comments 
at 14.
    \758\ WATT Comments at 14.
    \759\ R Street Institute Comments at 3.
    \760\ OMS Comments at 16.
---------------------------------------------------------------------------

    317. TAPS urges the Commission to allow interested persons to 
access transmission line ratings and methodologies through password-
protected interfaces, such as OASIS, such that if a transmission 
customer has concerns about the impact of a constraint, it should be 
able to obtain information on the transmission line ratings and 
methodologies used to establish such ratings. TAPS contends that doing 
so would enable transmission customers to better understand what is 
driving the prices that they are required to pay.\761\ APS states it 
would not support posting transmission line ratings and methodologies 
on OASIS, but would support other password-protected online forums 
where access could be controlled.\762\ To expand transmission line 
rating information and reduce the information gap, ACPA/SEIA suggests 
that there are several options, including expanding the FERC Form 715 
reporting requirements or making this information available on OASIS 
sites.\763\ DC Energy asks that the Commission require transmission 
owners outside of organized electricity markets to post transmission 
line ratings and methodologies on their OASIS pages or another 
password-protected online forum.\764\
---------------------------------------------------------------------------

    \761\ TAPS Comments at 24.
    \762\ APS Comments at 9.
    \763\ ACPA/SEIA Comments at 19-20.
    \764\ DC Energy Comments at 5-6.
---------------------------------------------------------------------------

    318. Clean Energy Parties contend that requiring transmission 
owners to disclose their transmission line ratings and methodologies to 
RTOs/ISOs and market monitors but not share with the broader public is 
unduly discriminatory.\765\ Exelon requests flexibility to allow 
transmission providers, like PJM, to publish transmission line ratings 
consistent with existing practices.\766\ ACPA/SEIA contends that the 
Commissions should require that all market participants have comparable 
information on near-term transmission service.\767\ ACPA/SEIA argues 
that because near-term transmission service information would only be 
available to transmission owners, RTOs/ISOs, and market monitors, there 
would be a discriminatory ``information gap,'' putting transmission 
customers at a disadvantage by not being able to easily identify 
optimal interconnection locations and not being able to understand or 
reproduce AAR or DLR congestion analyses.\768\
---------------------------------------------------------------------------

    \765\ Clean Energy Parties Comments at 14.
    \766\ Exelon Comments at 28-29.
    \767\ ACPA/SEIA Comments at 19-20.
    \768\ Id. at 18-19.
---------------------------------------------------------------------------

    319. New England State Agencies argue that it is important to 
states that

[[Page 2294]]

have relied on competitive procurements for certain types of energy 
development needs to have access to transmission line ratings and 
methodologies.\769\ According to New England State Agencies, the 
Commission's requirement in Order No. 1000 that transmission providers 
consider public policy transmission needs as part of regional 
transmission planning processes would be materially aided by allowing 
open access to transmission line ratings and similar data.\770\ New 
England State Agencies state that password protections and non-
disclosure agreements can be used in protecting confidential 
information in a wide variety of circumstances if there is concern 
about loss of confidential business information.\771\
---------------------------------------------------------------------------

    \769\ New England State Agencies Comments at 20.
    \770\ Id.
    \771\ Id.
---------------------------------------------------------------------------

    320. Conversely, several commenters oppose further sharing beyond 
transmission providers and, where appropriate, market monitors. 
PacifiCorp states that it strongly opposes making its transmission line 
ratings broadly available to stakeholders or posting such information 
to OASIS due to the potential for reliability risks and unclear 
benefits.\772\ MISO Transmission Owners state that there appears to be 
no need for transmission line ratings to be public because: (1) ATC is 
made available to the public; (2) transmission line ratings are only 
one of many inputs into ATC; and (3) ATC is made available on OASIS 
pages.\773\ PG&E recommends against requiring transmission owners and 
transmission providers to post real-time transmission line ratings on 
their OASIS pages, noting that transmission line rating methodologies 
should also not be disclosed to any parties other than the Commission 
and other transmission providers.\774\ Indicated PJM Transmission 
Owners argue that requiring transmission line ratings and methodologies 
to be made public would be unnecessary in PJM, given the existing 
information is made available.\775\ EEI recommends that the Commission 
not require transmission owners and transmission providers to post 
real-time transmission line ratings on their OASIS pages but instead 
provide only the methodologies for determining AARs and seasonal line 
ratings.\776\
---------------------------------------------------------------------------

    \772\ PacifiCorp Comments at 4.
    \773\ MISO Transmission Owners Comments at 37.
    \774\ PG&E Comments at 12.
    \775\ Indicated PJM Transmission Owners Comments at 23-24.
    \776\ EEI Comments at 13.
---------------------------------------------------------------------------

e. Auditing, Enforcement, and Litigation
    321. Several commenters note that NERC already audits transmission 
line ratings and argue that any transmission line ratings verification 
or transmission line ratings auditing performed by market monitors 
would be unnecessary or harmful.\777\ Exelon states that, were a market 
monitor to allege improper transmission line rating calculations which 
NERC has already approved, there could be dueling determinations and 
confusion and potential inconsistency with FPA section 215, which 
specifies that NERC, as the Electric Reliability Organization, is 
responsible for enforcing mandatory Reliability Standards.\778\ Exelon, 
AEP, and MISO Transmission Owners allege that calculating transmission 
line ratings requires a degree of engineering judgment, reflective of 
transmission owners' operational experience, risk tolerance, and local 
knowledge.\779\ Exelon argues that market monitors lack this 
knowledge.\780\ AEP argues that RTOs/ISOs should have no role beyond 
applying submitted transmission line ratings.\781\ EEI asks that the 
Commission emphasize that any final rule would not change the audit and 
enforcement construct already in place and that the audits should not 
specifically review the transmission line rating methodologies and 
assumptions.\782\ MISO Transmission Owners explain that it may not 
present a problem for RTOs/ISOs and market monitors to identify 
computational transmission line ratings errors, but RTOs/ISOs and 
market monitors should not be permitted to second-guess transmission 
line rating methodologies.\783\ Indicated PJM Transmission Owners 
explain that the functions of the PJM market monitor are limited to 
those items identified by Attachment M of the PJM OATT, requiring the 
market monitor to assess the competitiveness of the ``PJM markets, but 
not monitor transmission line ratings as it does not have the requisite 
expertise or reliability authority.\784\ Indicated PJM Transmission 
Owners disagree with the Commission's statement that the NERC 
Reliability Standards may be insufficient to ensure accurate 
transmission line ratings.\785\ Sunflower argues that the Commission 
should require specific measures for transmission providers to monitor 
the impact of AARs and seasonal line ratings on the safety and 
reliability of the electric system.\786\
---------------------------------------------------------------------------

    \777\ Exelon Comments at 24; AEP Comments at 8-9; EEI Comments 
at 13-14; Indicated PJM Transmission Owners Comments at 17-18.
    \778\ Exelon Comments at 25-26.
    \779\ Id. at 26-27; AEP Comments at 9; MISO Transmission Owners 
Comments at 37-38.
    \780\ Exelon Comments at 26-27.
    \781\ AEP Comments at 9.
    \782\ EEI Comments at 13-14.
    \783\ MISO Transmission Owners Comments at 37-38.
    \784\ Indicated PJM Transmission Owners Comments at 22-23.
    \785\ Id. at 19-21.
    \786\ Sunflower Comments at 4.
---------------------------------------------------------------------------

    322. Some commenters argue for further oversight and expansion of 
the auditing of transmission line ratings and methodologies. Potomac 
Economics recommends that the Commission require some form of 
independent oversight, verification, and monitoring of the transmission 
line ratings calculated and used in non-RTO/ISO areas.\787\ Potomac 
Economics contends that it is important to clarify that transmission 
line rating information that underlies curtailments under transmission 
line ratings or joint operating agreements be available to other 
transmission providers, reliability coordinators, or RTOs/ISOs that are 
affected by the curtailments.\788\ Ohio FEA recommends that PJM 
routinely review submitted transmission line ratings and the 
methodologies used in their development; otherwise, Ohio FEA continues, 
the benefits associated with implementing AARs may prove to be illusory 
if the transmission line ratings themselves are not based on objective 
and accurate criteria.\789\ Ohio FEA insists that the PJM market 
monitor must be granted the authority to review transmission line 
ratings and take corrective actions deemed necessary if the market 
monitor concludes that a transmission owner's transmission line ratings 
are inaccurate, consistent with the market monitor's role as defined in 
Attachment M of the PJM OATT.\790\
---------------------------------------------------------------------------

    \787\ Potomac Economics Comments at 18; see also Potomac 
Economics Reply Comments at 12.
    \788\ Potomac Economics Comments at 18.
    \789\ Ohio FEA Comments at 5-6.
    \790\ Id. at 6.
---------------------------------------------------------------------------

    323. Many commenters express concern over potential litigation 
regarding transmission line ratings and methodologies (though AEP 
states that the proposed requirements in the NOPR adequately mitigate 
litigation risks).\791\ EEI argues that third parties should not be 
able to litigate or dispute transmission line ratings or 
methodologies.\792\ Exelon caveats that its position supporting 
additional transparency is contingent on the Commission ensuring that 
the enhanced transparency does not result in constant litigation from 
market participants, provided such transmission line ratings

[[Page 2295]]

and calculations are reasonably accurate at reflecting a transmission 
facility's power transfer capability, as transmission line ratings are 
fundamentally a reliability concept.\793\ MISO Transmission Owners 
argue that transparency requirements beyond those proposed in the NOPR 
that result in an increase in disputes and litigation surrounding 
transmission line ratings and/or methodologies would reduce the 
benefits of the proposed reforms. MISO Transmission Owners therefore 
contend that the Commission should clarify its statement in the NOPR 
that the proposed increased transparency will allow RTOs/ISOs and 
market monitors to verify transmission line ratings.\794\ Similarly, 
Indicated PJM Transmission Owners warn that further transparency 
disclosure requirements would result in costly and time consuming 
litigation, and thereby increased burdens on transmission owners and 
the Commission, as a result of arguments from market participants 
soliciting changes designed to benefit themselves and negatively affect 
others. Indicated PJM Transmission Owners stress that this would be 
inappropriate because transmission line ratings are complex 
calculations, based on many different factors, including local assets, 
engineering judgment, and how assets are traditionally operated, and 
therefore litigation with the Commission would be inappropriate.\795\ 
ITC requests that the final rule clarify that incorrect transmission 
line ratings due to changes in weather or unintentional errors in data 
that were submitted in good faith should not create additional legal or 
regulatory liability for transmission owners. ITC states that it would 
not benefit from such errors since it is primarily concerned with 
reliability and does not participate in markets.\796\ Conversely to 
these commenters, AEP expresses that the Commission's NOPR strikes the 
right balance between providing transparency without creating risks of 
unnecessary litigation for transmission owners if transmission line 
ratings cannot be precisely replicated by third parties.\797\ 
Furthermore, DC Energy contends that the need for disclosure outweighs 
transmission owners' claims of confidentiality or fear of potential 
litigation.\798\
---------------------------------------------------------------------------

    \791\ AEP Comments at 10.
    \792\ EEI Comments at 13-14.
    \793\ Exelon Comments at 29.
    \794\ MISO Transmission Owners Comments at 37-38 (citing NOPR, 
173 FERC ] 61,165 at P 127).
    \795\ Indicated PJM Transmission Owners Comment at 24.
    \796\ ITC Comments at 16.
    \797\ AEP Comments at 9-10.
    \798\ DC Energy Comments at 5.
---------------------------------------------------------------------------

f. Posting of Exceptions to OASIS
    324. EPSA asks that transmission providers be required to disclose 
(potentially via OASIS) which transmission lines they deem as not 
benefitting from an AAR or seasonal line rating. EPSA also asks that 
transmission providers be required to disclose the reasons for making 
those determinations to thereby enable RTOs/ISOs and market monitors to 
verify those decisions. Moreover, EPSA asks that these decisions be 
evaluated at least every five years to ensure AAR-exempt transmission 
lines should continue to qualify for exceptions.\799\
---------------------------------------------------------------------------

    \799\ EPSA Comments at 4.
---------------------------------------------------------------------------

g. Other Transparency Topics
    325. ISO-NE states that to comply with the NOPR's proposed 
transparency requirements, it would need to modify Planning Procedure 
No. 7, Procedures for Determining and Implementing Transmission 
Facility Ratings (PP7) as New England Transmission Owners are required 
to follow the PP7 procedures to determine transmission line rating 
methodologies.\800\ ISO-NE requests that the Commission allow for 
sufficient time for the PP7 changes to make their way through the 
applicable processes for the transmission owners to implement those 
changes and then provide new transmission line ratings to ISO-NE and 
its market monitor in the manner contemplated in the NOPR.\801\
---------------------------------------------------------------------------

    \800\ ISO-NE Comments at 11.
    \801\ Id. at 11.
---------------------------------------------------------------------------

    326. NRECA/LPPC recommend that any measures in the final rule to 
improve the transparency of transmission line ratings should be 
consistent with the requirements of existing mandatory NERC Reliability 
Standards, including Critical Infrastructure Protection (CIP) 
Standards, as well as requirements to protect Critical Electric/Energy 
Infrastructure Information (CEII).\802\
---------------------------------------------------------------------------

    \802\ NRECA/LPPC Comments at 3.
---------------------------------------------------------------------------

    327. OMS suggests that the Commission could revisit the data it 
currently collects in FERC Form 715 to better analyze how the data 
already being collected can be used to understand some transmission 
owners' transmission line ratings and methodologies but not 
others.\803\ OMS also suggests that the Commission consider a comment 
and response process between transmission owners, transmission 
providers, and market monitors to provide additional oversight into the 
appropriateness of transmission line ratings throughout the bulk power 
system.\804\
---------------------------------------------------------------------------

    \803\ OMS Comments at 17.
    \804\ Id.
---------------------------------------------------------------------------

    328. Clean Energy Parties contend that RTOs/ISOs should be required 
to discuss with stakeholders and report to the Commission how winter 
capacity deliverability differs from summer and identify possible 
reliability improvements or cost savings arising from those 
differences.\805\
---------------------------------------------------------------------------

    \805\ Clean Energy Parties Comments at 12.
---------------------------------------------------------------------------

    329. Some commenters assert a connection between transparency 
around transmission line ratings and FTR markets. EDFR states that 
transparency provides market participants with a better understanding 
of how transmission line ratings could change over time while helping 
to anticipate congestion, hedge congestion, and participate in the FTR 
markets.\806\ DC Energy states that market participants, particularly 
those that purchase and sell FTRs, need transparency in order to 
critically analyze and address market inefficiencies.\807\ DC Energy 
contends that FTR market participants will require transparent 
transmission line rating and methodology information in order to 
accurately forecast congestion.\808\ DC Energy asserts that 
transparency is essential for the transition to AARs and DLRs because, 
without adequate transparency, AARs and DLRs could actually make 
congestion hedges less accurate. This is because, according to DC 
Energy, AARs and DLRs will cause transmission line ratings to change 
without advance notification and, in times of adverse system 
conditions, AARs and DLRs will more accurately reflect the fact that 
less transfer capability is available.\809\
---------------------------------------------------------------------------

    \806\ EDFR Comments at 7.
    \807\ DC Energy Comments at 3-4.
    \808\ Id. at 4.
    \809\ Id. at 5.
---------------------------------------------------------------------------

3. Commission Determination
    330. Upon consideration of the comments received, we adopt the NOPR 
proposal to require public utility transmission owners to share their 
transmission line ratings for each period for which they are calculated 
and transmission line rating methodologies with their transmission 
providers and with market monitors in RTOs/ISOs. We acknowledge 
situations in which the transmission owner and transmission provider 
are the same entity, and we expect that in such cases compliance with 
this final rule's transparency requirements will be simple in the sense 
that the transmission provider will not have to rely on a separate 
transmission

[[Page 2296]]

owner to provide the transmission line ratings and methodologies. We 
also adopt three additional transparency requirements. First, we 
require each transmission provider to share transmission line ratings 
and methodologies with any transmission provider(s) upon request. 
Second, we require each transmission provider to maintain a database of 
its transmission line ratings and methodologies on the transmission 
provider's OASIS site, or other password-protected website. We require 
that this database be in such a form that can be accessed by all 
parties with OASIS access or access to the password-protected website. 
The database should archive and allow for querying of all current 
transmission line ratings and all transmission line ratings used in the 
past five years. Third, we require transmission providers to post on 
OASIS, or other password-protected website, which transmission lines 
qualify for an exception to the AAR or seasonal line rating 
requirements and the reasons why such transmission lines qualify for an 
exception.
a. Transmission Owners Sharing Ratings and Methodologies With 
Transmission Providers and, Where Applicable, Market Monitors
    331. We find that requiring public utility transmission owners to 
share transmission line ratings and methodologies with their 
transmission providers and, in RTOs/ISOs, market monitors, will help 
remedy unjust and unreasonable wholesale rates caused by inaccurate 
transmission line ratings. We affirm the Commission's preliminary 
finding in the NOPR that this requirement will enhance operational and 
situational awareness by ensuring that transmission providers know the 
effect that changes in ambient air temperature would have on 
transmission line ratings within their system.\810\ Further, as the 
Commission explained in the NOPR, this requirement will provide 
transmission providers and market monitor(s) the information necessary 
to verify the resulting transmission line ratings and to identify 
potential errors.\811\
---------------------------------------------------------------------------

    \810\ NOPR, 173 FERC ] 61,165 at P 127.
    \811\ Id.
---------------------------------------------------------------------------

    332. We agree with EDFR that the transparency-increasing effects of 
requiring public utility transmission owners to share transmission line 
ratings and methodologies with their transmission provider(s), and with 
market monitors in RTOs/ISOs, will result in more accurate transmission 
line ratings. By sharing transmission line ratings and methodologies 
with transmission providers and market monitors, these parties will be 
better positioned to develop automated screens and other techniques to 
detect corrupted data or other errors that could negatively impact 
operations or planning processes.
    333. We disagree with arguments that because transmission line 
ratings are reliability tools that are effectively overseen by NERC, 
additional transparency requirements are unnecessary. While 
transmission line ratings are an important reliability tool, we find 
(as discussed above in Section III) that transmission line ratings 
directly affect wholesale rates. Further, commenters have not explained 
why a relationship between transmission line ratings and reliability 
would represent a reason not to adopt the transparency requirements. We 
also disagree with comments that requiring public utility transmission 
owners to share transmission line ratings and methodologies with their 
transmission provider(s) and with market monitors in RTOs/ISOs would be 
unduly burdensome and could create inconsistencies between transmission 
line ratings used internally by transmission owners and transmission 
line ratings used by transmission providers. We recognize comments from 
New England State Agencies noting that such disclosure is already 
common in some markets, and that this indicates that transmission 
owners can comply without undue difficulty.\812\ Moreover, we think it 
is unlikely that sharing of transmission line ratings would create 
inconsistencies in the manner described by ITC. On the contrary, we 
believe that a benefit of this requirement would be to identify and 
promote the resolution of such inconsistencies.
---------------------------------------------------------------------------

    \812\ New England State Agencies Comments at 20.
---------------------------------------------------------------------------

    334. Finally, we reiterate that the Commission will continue to 
conduct reviews of transmission line ratings as a component of broader 
tariff compliance audits \813\ and that this final rule does not change 
the auditing requirements or authorities of any entity.
---------------------------------------------------------------------------

    \813\ Many commenters use the term ``audit'' to describe 
activities by market monitors and other entities that the 
Commission's rules do not define as auditing. We note that the 
Commission retains its authority to formally audit for compliance 
with OATTs and other Commission-jurisdictional rules.
---------------------------------------------------------------------------

b. Transmission Providers Sharing With Any Transmission Provider(s) 
Upon Request
    335. As set forth under ``Obligations of Transmission Provider'' in 
pro forma OATT Attachment M, we further require transmission providers 
to share transmission line ratings and methodologies with any 
transmission provider(s) upon request and in a timely manner. We agree 
with commenters that contend that this requirement is necessary because 
transmission operators often consider the effect that power flows on 
their transmission lines will have on other transmission providers' 
transmission lines, and transmission providers will need transmission 
line ratings on other systems to evaluate these effects properly. While 
we acknowledge that Vistra's example involved neighboring transmission 
providers, we do not limit this requirement to neighboring transmission 
providers, as such power flow effects can sometimes extend beyond 
neighboring transmission providers (particularly if a neighboring 
transmission provider's system is geographically/electrically narrow 
where it approaches another transmission provider's system). Further, 
we agree with commenters that this information sharing could take 
several forms, and that the Commission need not dictate an information 
sharing method. However, any such information sharing method should be 
sufficient to accommodate the reasonable business needs of the other 
transmission provider(s) (e.g., to allow the other transmission 
provider(s) to process transmission service requests in a timely 
manner).
c. Transmission Providers Sharing With Other Entities
    336. We further require each transmission provider to maintain a 
database of their transmission owners' transmission line ratings and 
methodologies on the password-protected section of their OASIS site or 
other password-protected website. This requirement will allow other 
entities (beyond transmission providers and market monitors) that are 
able to access the password-protected section of the transmission 
provider's OASIS site or other password-protected website to have 
access to the database of transmission line ratings and methodologies. 
This requirement is set forth under ``Obligations of Transmission 
Provider'' in pro forma OATT Attachment M. We agree with commenters 
that making transmission line ratings and methodologies available to a 
broader range of stakeholders will amplify the expected benefits of the 
proposal included in the NOPR, further facilitate more accurate 
transmission line ratings, and facilitate more cost-effective decisions 
by market participants and, as described by New England State Agencies, 
state agencies. For example, without accurate

[[Page 2297]]

transmission line rating information, market participants may be unable 
to make informed siting decisions regarding where to build generation 
or where to site load. Also, without accurate transmission line rating 
information, market participants may be unable to accurately predict 
and hedge against transmission congestion. Moreover, as New England 
State Agencies argue, access to transmission line ratings and 
transmission line rating methodologies is important to states that have 
relied on competitive procurements for certain types of energy 
development needs.\814\ We acknowledge that requiring this information 
to be placed on OASIS or other password-protected website presents a 
burden on transmission providers, but we find that the benefits of 
increased transparency are likely to outweigh any such burden.
---------------------------------------------------------------------------

    \814\ New England State Agencies Comments at 20.
---------------------------------------------------------------------------

    337. Beyond enhancing the general benefits of the transmission line 
rating requirements adopted herein, we find that transparency for 
transmission line ratings and methodologies will also be particularly 
beneficial to wholesale market participants trying to manage 
uncertainty. With respect to FTR market participants, for example, we 
agree with DC Energy that, because FTR payouts are based on congestion 
costs that change with transmission line ratings, sharing transmission 
line ratings and methodologies with a wider range of stakeholders will 
help establish efficient FTR market price discovery by improving FTR 
market participants' understanding of certain drivers of congestion, 
and allow such market participants to build such understanding into 
their FTR bids and offers.\815\
---------------------------------------------------------------------------

    \815\ DC Energy Comments at 3. While different RTOs/ISOs have 
different names for these financial products, such as financial 
transmission rights, transmission congestion rights, congestion 
revenue rights, etc., for simplicity here we will use FTRs to refer 
to any such financial product in the RTOs/ISOs.
---------------------------------------------------------------------------

    338. We disagree with arguments contending that requiring each 
transmission provider to maintain a database of each transmission 
owner's transmission line ratings and methodologies on the transmission 
provider's OASIS site or other password-protected website will lead to 
unjust and unreasonable wholesale rates or other undesirable outcomes. 
Specifically, we are not persuaded by comments that making transmission 
line ratings and methodologies available to a broader range of 
stakeholders could result in increased litigation whereby customers 
initiate complaints against transmission owners regarding the 
underlying assumptions used to calculate transmission line ratings or 
regarding the calculations themselves. There is a lack of evidence of 
increased litigation in those regions where disclosure is already 
common, as noted by the New England State Agencies.\816\ Moreover, 
commenters have not identified any complaints or other such litigation 
about transmission line ratings related to this existing requirement. 
Further, consistent with the Commission's statement in the NOPR,\817\ 
we intend to give latitude to transmission owners to determine their 
transmission line ratings in accordance with good utility practice. 
Finally, we note that section 37.6 of the Commission's regulations 
already requires transmission providers, upon customer request, to make 
all data used to calculate ATC for any constrained posted path publicly 
available on OASIS. This includes the limiting elements and the cause 
of the limit (e.g., thermal, voltage, stability), as well as load 
forecast assumptions.\818\ The posting requirement for transmission 
line ratings and methodologies is consistent with that existing 
requirement.
---------------------------------------------------------------------------

    \816\ New England State Agencies Comments at 20.
    \817\ NOPR, 173 FERC ] 61,165 at PP 98, 105.
    \818\ See 18 CFR 37.6.
---------------------------------------------------------------------------

    339. Transmission line ratings stored in the required database must 
include a full record of all transmission line ratings, both as used in 
real-time operations, and as used for all future market periods for 
which transmission service is offered. For example, a transmission 
provider that implements AARs calculated for the next 240 hours (for 
use in evaluating near-term transmission service requests), re-
calculates such AARs every hour, and calculates seasonal line ratings 
(for use in evaluating longer-term transmission service requests) would 
keep records of its transmission line ratings in the following manner. 
With respect to its AARs, such a transmission provider would insert 
records into its transmission line rating database each hour, shortly 
after calculation of its AARs. In each such hour, the transmission 
provider would insert a separate AAR record into its database for: (1) 
Each transmission line; (2) each current and forward hour for which 
transmission line ratings are calculated (at least one rating for each 
of the 240 hours in the next 10 days); and (3) each rating type (normal 
and each type of emergency rating (e.g., 30 minute, one hour, etc.)). 
If such a transmission provider had 1,000 transmission lines and four 
rating types (e.g., normal, 30 minute, one hour, and four hour), then 
each hour the transmission provider would insert into its database 
960,000 new AAR records (1000 x 240 x 4).\819\ Furthermore, such a 
transmission provider would also maintain in its database records of 
which seasonal line ratings (for use in evaluating longer-term 
transmission service requests) or other types of transmission line 
ratings (as permitted under pro forma OATT Attachment M, e.g., static 
line ratings) were in effect at which times for each transmission 
line.\820\ Finally, while we are not requiring implementation of DLRs 
at this time, we note that if a transmission provider implements DLRs 
on any of its transmission lines, then under this requirement it would 
document the DLR ratings on such transmission lines in the same way 
that it documents its AAR ratings, as discussed above.
---------------------------------------------------------------------------

    \819\ We note that transmission providers may determine that 
there are more efficient ways of storing the AAR data than presented 
in the example above, and such approaches may be acceptable as long 
as users of the database can readily identify which such ratings 
(including for the operational hour and any forward hours) were in 
effect for which transmission lines at which times.
    \820\ We do not specify exactly how records of seasonal or 
static line ratings should be stored in the line rating database. 
However, such longer-term transmission line ratings do not 
necessarily need to be stored on an hourly basis, so long as users 
of the database can readily identify which such ratings were in 
effect for which transmission lines at which times. We note that 
some transmission lines may not have any AAR ratings at all, where 
permitted under pro forma OATT Attachment M, and so may only have 
ratings such as seasonal or static line ratings.
---------------------------------------------------------------------------

    340. Transmission providers must maintain in their database records 
of which transmission line ratings and methodologies were in effect at 
which times over at least the previous five years. This five-year 
period of record retention is consistent with other document retention 
periods required for OASIS postings.\821\ Each record in the database 
must indicate to which transmission line the record applies, and the 
date and time the record was entered into the database. Finally, the 
database must be maintained such that users can view, download, and 
query data in standard formats, using standard protocols.
---------------------------------------------------------------------------

    \821\ 18 CFR 37.6 (Information to be posted on the OASIS).
---------------------------------------------------------------------------

d. Transmission Providers Posting Exceptions and Temporary Alternate 
Ratings to OASIS
    341. Finally, in response to EPSA, we require transmission 
providers to make postings to the database of transmission line ratings 
on their OASIS site or other password-protected website (discussed 
above in Section IV.G.3.d) documenting

[[Page 2298]]

any uses of exceptions (under the ``Exceptions'' paragraph of pro forma 
OATT Attachment M) or temporary alternate ratings (under the ``System 
Reliability'' section of pro forma OATT Attachment M). This requirement 
to post exceptions and temporary alternate ratings on OASIS or other 
password-protected website is set forth in pro forma OATT Attachment M. 
We require that such postings document the nature of and basis for each 
such exception or alternate rating, as well as the date(s) and time(s) 
of initiation and (if applicable) withdrawal for the exception or the 
alternate rating.
    342. We find that the requirement for such postings will help 
ensure proper transparency for the use of such exceptions and temporary 
alternate ratings, similar to the transparency provided through other 
posting requirements of this final rule.\822\ Furthermore, these 
postings of exceptions will support the fulfillment of and verification 
of compliance with the requirement, discussed above in Section IV.D.3, 
that exceptions be re-evaluated at least every five years.
---------------------------------------------------------------------------

    \822\ See, 18 CFR 37.6 (Information to be posted on the OASIS).
---------------------------------------------------------------------------

    343. Similar to the benefits discussed above in Section IV.G.3.c 
related to requiring transmission line ratings and methodologies to be 
available on OASIS sites or other password-protected websites, we find 
that this requirement for exceptions postings will enable and support 
verification of the accuracy of transmission line ratings.

H. Other Miscellaneous Issues

1. Comments
    344. Some commenters argue for incentives to encourage DLR 
deployment. Specifically, NYTOs and ACORE request financial incentives 
for AARs and DLRs under FPA section 219.\823\ ACPA/SEIA contend that 
the Commission should consider accelerated cost recovery of 
depreciation to implement sensor-based DLRs.\824\ Although WATT urges 
the Commission to address the misalignment of incentives to adopt DLRs 
or other grid-enhancing technologies, WATT asserts that the Commission 
should not grant incentives for DLRs in this docket.\825\
---------------------------------------------------------------------------

    \823\ NYTOs Comments at 2; ACORE Comments at 3-4.
    \824\ ACPA/SEIA Comments at 11.
    \825\ WATT Comments at 16.
---------------------------------------------------------------------------

    345. MISO contends that while AARs may provide incremental transfer 
capability on existing transmission lines, they cannot solve 
significant long-range transmission problems.\826\ Moreover, EEI argues 
that chronic congestion should be reviewed and alleviated in the 
transmission planning process.\827\
---------------------------------------------------------------------------

    \826\ MISO Comments at 2, 6-7.
    \827\ EEI Comments at 6.
---------------------------------------------------------------------------

2. Commission Determination
    346. In response to arguments about incentives for advanced 
transmission technology deployment, we find such arguments about 
incentivizing certain technology to be outside the scope of this 
proceeding, which is limited to the Commission's proposed requirements 
for transmission line ratings.
    347. In response to MISO's assertion that AARs cannot solve 
significant long-range transmission problems, we find transmission 
planning and development to be outside the scope of this proceeding. 
For the same reason, we find EEI's claim that chronic congestion should 
be reviewed and alleviated in the transmission planning process to be 
outside the scope of this proceeding. We note that the Commission 
recently initiated a proceeding to examine a broad range of 
transmission-related issues, including regional transmission planning, 
in its July 2021 Advance Notice of Proposed Rulemaking in Docket No. 
RM21-17-000.\828\
---------------------------------------------------------------------------

    \828\ Building for the Future Through Electric Regional 
Transmission Planning and Cost Allocation and Generator 
Interconnection, 86 FR 40266 (July 27, 2021), 176 FERC ] 61,024 
(2021).
---------------------------------------------------------------------------

I. Compliance

1. NOPR Proposal
    348. In the NOPR, the Commission proposed to require each 
transmission provider to submit a compliance filing within 60 days of 
the effective date of any final rule. The Commission clarified that 
this compliance deadline would be for transmission providers to submit 
proposed AAR tariff changes, RTOs/ISOs to submit proposed tariff 
changes designed to maintain systems and procedures needed to allow for 
the use of AARs and DLRs, transmission owners to submit tariff changes 
implementing the proposed transparency reforms, or for each entity to 
otherwise comply with any final rule. As justification, the Commission 
acknowledged that implementing the reforms required by any final rule 
in this proceeding may be complex, but preliminarily found that 
implementation of these reforms is important to ensure wholesale rates 
are just and reasonable.
    349. Recognizing the complexity of the proposed AAR requirements, 
the Commission proposed a staggered implementation approach that would 
prioritize implementation on historically congested transmission lines 
(within one year from the date of the compliance filing), but further 
proposed a less aggressive implementation of AARs on all other 
transmission lines (within two years from the date of the compliance 
filing). For the proposed DLR requirements and proposed transparency 
requirements, the Commission proposed that tariff changes filed in 
response to a final rule in this proceeding would become effective 
within one year from the date of the compliance filing.
    350. The Commission recognized that some transmission providers may 
have provisions in their existing OATTs or other document(s) subject to 
the Commission's jurisdiction that the Commission has deemed to be 
consistent with or superior to the pro forma OATT or that are 
permissible under the independent entity variation standard or regional 
reliability standard. Where these provisions would be modified, the 
Commission proposed to require transmission providers to either comply 
with the proposed requirements or demonstrate that these previously 
approved variations continue to be consistent with or superior to the 
pro forma OATT as modified by the proposed requirements or demonstrate 
that these previously approved variations are just and reasonable and 
meet the purpose of the final rule under the independent entity 
variation standard or regional reliability standard.\829\
---------------------------------------------------------------------------

    \829\ NOPR, 173 FERC ] 61,165 at P 132.
---------------------------------------------------------------------------

2. Comments
    351. Comments on the proposed compliance and implementation 
timelines came predominately from RTOs/ISOs and transmission owners 
requesting more time. Most commenters suggest a minimum 120-day 
compliance deadline,\830\ but some suggest a minimum 180-day compliance 
deadline,\831\ and others suggest a minimum 90-day compliance 
deadline.\832\ Most transmission owners commenting argue that three 
years is needed to implement AARs on priority transmission lines; \833\ 
however,

[[Page 2299]]

PacifiCorp suggests that two years would be sufficient, while PG&E 
suggests that at least four years would be needed.\834\ NYTOs, WAPA, 
and BPA also contend that the proposed implementation timeline is 
insufficient but do not proposed an alternative schedule.\835\ Some 
commenters support the proposed timeline.\836\ Industrial Customer 
Organizations recommend that the proposed implementation timeline be 
halved.\837\
---------------------------------------------------------------------------

    \830\ EEI Comments at 19; NRECA/LPPC Comments at 28-29; MISO 
Transmission Owners Comments at 38-39; SCE Comments at 2; SDG&E 
Comments at 1-2; APS Comments at 10; WFEC Comments at 1; Southern 
Company Comments at 6-7; MISO Comments at 31; ISO-NE Comments at 12.
    \831\ CAISO Comments at 2; NYISO Comments at 18.
    \832\ SPP Comments at 16; PacifiCorp Comments at 7.
    \833\ EEI Comments at 18; NRECA/LPPC Comments at 28-29; MISO 
Transmission Owners Comments at 22-23; SCE Comments at 2; SDG&E 
Comments at 1-2; APS Comments at 10; WFEC Comments at 1; Southern 
Company Comments at 6-7; ITC Comments at 5; LADWP Comments at 8-9.
    \834\ PacifiCorp Comments at 2-3; PG&E Comments at 6-8.
    \835\ NYTOs Comments at 1; WAPA Comments at 6; BPA Comments at 
6.
    \836\ OMS Comments at 9; Potomac Economics Comments at 19-20.
    \837\ Industrial Customer Organizations Comments at 22.
---------------------------------------------------------------------------

    352. Arguing that one year is insufficient to implement AARs on 
historically congested transmission lines, MISO Transmission Owners 
explain that their experience is that, on average, it takes several 
years to implement AARs on even a subset of transmission lines.\838\ 
According to MISO Transmission Owners, at least three years is needed 
for AAR implementation because of all the steps needed to implement 
AARs, including developing and updating the transmission line rating 
methodologies, analyzing historical weather information, identifying 
limiting elements, developing a transmission line ratings database, 
updating the transmission management system, testing the transmission 
line ratings, and linking the transmission owners' transmission 
management system to the RTO/ISO EMS, all while maintaining 
cybersecurity standards.\839\ EEI similarly states that it could take 
up to two years just to upgrade operating and data systems to create 
the capability to produce and update AAR calculations.\840\ Southern 
Company and SCE support EEI's comments.\841\ Specifically, Southern 
Company requests at least 120 days for compliance filings and at least 
three years for AAR implementation.\842\ SCE claims that the 
Commission's proposed implementation schedule is not realistic.\843\
---------------------------------------------------------------------------

    \838\ MISO Transmission Owners Comments at 22.
    \839\ Id.
    \840\ EEI Comments at 18.
    \841\ Southern Company Comments at 3-4; SCE Comments at 2.
    \842\ Southern Company Comments at 3-4.
    \843\ SCE Comments at 2.
---------------------------------------------------------------------------

    353. PacifiCorp states that implementation of the NOPR proposal 
would be complicated as it would require updates to PacifiCorp's EMS, 
SCADA, and other software that communicates transmission line ratings 
with CAISO, RC West, and other transmission providers.\844\ APS argues 
that adequate time is needed to develop the business requirements for 
the software vendors and that APS will have to work with multiple 
software vendors to comply with the TLR provisions as currently 
delineated in the NOPR.\845\ NRECA states that its members need a 
minimum of three years to implement AARs on all their transmission 
lines in order to identify, document, and implement the necessary 
system and process changes.\846\ Presenting a five year implementation 
approach, PG&E states that AAR implementation will require significant 
initial investments and that the Commission should allow for sufficient 
time for RTOs/ISOs and transmission owners to collaborate to develop 
new communication systems and new processes for determining and 
operating with AARs.\847\
---------------------------------------------------------------------------

    \844\ PacifiCorp Comments at 3-4.
    \845\ APS Comments at 6.
    \846\ NRECA/LPPC Comments at 28-29.
    \847\ PG&E Comments at 6-7.
---------------------------------------------------------------------------

    354. ITC states that the proposed requirements in the NOPR would be 
complicated to implement for transmission owners that currently do not 
use AARs, and the implementation timeline would exceed one year since 
it would require coordination with the transmission management system, 
development of internal transmission line ratings software or a 
software purchase from a vendor, and analysis of how AARs will affect 
ITC's internal transmission line ratings database.\848\ The proposed 
one-year implementation timelines suggest that ITC would need to first 
develop a costly and error-prone manual process as a short-term 
solution before developing a more permanent automated process.\849\ ITC 
states that additional time should be built into the Commission's 
proposed timeline so that initial implementation issues can be 
identified and corrected.\850\ Similarly, NYTOs argue that the one-year 
compliance timeline for AARs is overly ambitious and could have adverse 
effects, be costly, and potentially impossible.\851\
---------------------------------------------------------------------------

    \848\ ITC Comments at 6.
    \849\ Id. at 6-7.
    \850\ Id. at 7.
    \851\ NYTOs Comments at 1.
---------------------------------------------------------------------------

    355. Other transmission owners voicing concern with the proposed 
schedule include WAPA, LADWP, and BPA. WAPA notes that it is concerned 
about the proposed timeline, given its expansive geographic area and 
transmission system of over 17,000 line miles, and its other statutory 
duties it must meet to operate its system reliably.\852\ LADWP 
recommends an implementation period of no less than three years for 
congested transmission lines, noting that the proposed AAR requirements 
will necessitate extensive re-negotiations of long-term reservation 
rights and arguing that the AAR implementation timeline is not 
sufficient to address challenges associated with calculating hourly ATC 
based on AARs, including development of additional reliability tools 
and ongoing maintenance of these tools by additional skilled 
employees.\853\ Similarly, BPA asserts that the proposed implementation 
period is too short because it fails to account for the different 
transmission provider service territory sizes and for the complexity of 
AAR implementation.\854\
---------------------------------------------------------------------------

    \852\ WAPA Comments at 6.
    \853\ LADWP Comments at 8-9.
    \854\ BPA Comments at 6.
---------------------------------------------------------------------------

    356. However, according to OMS, the deadlines seem to be reasonable 
and necessary. OMS states that: MISO Transmission Owners are already 
working on implementing AARs; since 2016, MISO has had an Integrated 
Roadmap item called ``Application of Forecasted and Real-time Ambient 
Adjusted Ratings'' ranked as a high priority in MISO's 2021 Integrated 
Roadmap Work Plan; and, because MISO Transmission Owners have begun 
developing a framework to identify candidate AAR facilities based on 
historical congestion, they should have already begun phase one 
compliance.\855\ Industrial Customer Organizations similarly state that 
transmission owners should begin AAR implementation now and that, 
without strict deadlines, AAR implementation before 2022 is 
unlikely.\856\
---------------------------------------------------------------------------

    \855\ OMS Comments at 9.
    \856\ Industrial Customer Organizations Comments at 22.
---------------------------------------------------------------------------

    357. RTOs/ISOs generally request additional implementation 
time.\857\ CAISO claims that the compliance schedule set forth in the 
NOPR is neither realistic nor achievable because the proposal for 
hourly updates to transmission line ratings will require additional 
market design changes and significant technology enhancements. For the 
implementation schedule, CAISO requests an additional 18 months from 
the submission of a compliance filing, explaining that implementation 
will require technology

[[Page 2300]]

enhancements necessary to automate the submission and use of hourly 
adjusted transmission line ratings.\858\ SPP contends that 60 days 
would be insufficient time for SPP to complete its stakeholder process 
to review any proposed tariff language and notes that, depending on the 
changes, the process would take at least three months. For 
implementation, SPP requests an additional two years from the 
submission of a compliance filing.\859\ ISO-NE explains that it will 
need to upgrade its systems to accept hourly transmission line ratings, 
and that it does not believe one year would be enough time to do so, 
but does not propose a timeline.\860\ Additionally, ISO-NE asks for 
sufficient time to analyze how AARs would impact the emergency ratings 
currently employed and flexibility in implementation timing, and states 
that an update to the overall rating methodology to include AARs may 
also necessitate the need for new emergency ratings based on those 
AARs.\861\ MISO states that it would be able to implement the NOPR 
proposal in the real-time market in a year, but states that it would 
need until mid-2023 and the end of 2024 to implement the NOPR proposal 
in the day-ahead market and Intra-day and Foreword Reliability 
Assessment Commitment respectively.\862\ NYISO requests flexibility for 
each RTO/ISO to develop its own implementation schedule,\863\ arguing 
that the AAR schedule proposed is not enough time to develop the 
significant changes to software and rules needed,\864\ and stating that 
it could incur significant risk and expense if it is required to comply 
within the proposed one to two years.\865\ PJM, however, states that, 
while the NOPR proposal will likely require some additional system 
changes and data validation to comply, it believes the time proposed 
would be sufficient.\866\
---------------------------------------------------------------------------

    \857\ CAISO Comments at 2; ISO-NE Comments at 8; SPP Comments at 
10; MISO Comments at 30-32; NYISO Comments at 16-18.
    \858\ CAISO Comments at 2.
    \859\ SPP Comments at 10.
    \860\ ISO-NE Comments at 8.
    \861\ Id. at 11.
    \862\ MISO Comments at 30-32.
    \863\ NYISO Comments at 16.
    \864\ Id. at 18.
    \865\ Id. at 19.
    \866\ PJM Comments at 8.
---------------------------------------------------------------------------

    358. Potomac Economics states that clarification may be needed as 
to whether the requirements for automation are on the transmission line 
rating submission process and use of AARs or the entire transmission 
line rating process. Potomac Economics states that requiring full 
automation may delay implementation and may not be appropriate for all 
transmission owners.\867\
---------------------------------------------------------------------------

    \867\ Potomac Economics Comments at 19.
---------------------------------------------------------------------------

    359. Finally, PJM requests clarity that public utilities are able 
to demonstrate compliance via the independent entity variation 
standard, regional reliability standard, or demonstrate that their 
existing rules are consistent with or superior to the reforms adopted 
by the Commission.\868\
---------------------------------------------------------------------------

    \868\ PJM Comments at 15.
---------------------------------------------------------------------------

3. Commission Determination
    360. Upon consideration of the comments received, we modify the 
compliance deadline proposed in the NOPR. Instead of 60 days, we 
require each transmission provider to submit a compliance filing within 
120 days of the effective date of this final rule. We clarify that this 
compliance deadline is for transmission providers to revise their OATTs 
to incorporate pro forma OATT Attachment M. We agree with EEI's 
compliance recommendation \869\ and find that 120 days will be 
sufficient to allow for a robust stakeholder evaluation and development 
of revised tariff language to comply with the requirements adopted in 
this final rule.
---------------------------------------------------------------------------

    \869\ EEI Comments at 19.
---------------------------------------------------------------------------

    361. In addition, we modify the proposed implementation schedule. 
Instead of the proposed one-year/two-year staggered implementation 
timeline based on priority, we require that all requirements adopted 
herein be implemented no later than three years from the compliance 
filing due date. Three years is consistent with the implementation 
schedule most commonly suggested by transmission owners for AAR 
implementation on priority transmission lines.\870\ We find that three 
years should be sufficient time for transmission owners and 
transmission providers to implement changes to their processes and 
systems to comply with the requirements adopted in this final rule.
---------------------------------------------------------------------------

    \870\ Id. at 18; NRECA/LPPC Comments at 28-29; MISO Transmission 
Owners Comments at 22-23; SCE Comments at 2; SDG&E Comments at 1-2; 
APS Comments at 10; WFEC Comments at 1; Southern Company Comments at 
6-7; ITC Comments at 5; LADWP Comments at 8-9.
---------------------------------------------------------------------------

    362. In response to comments about automation from Potomac 
Economics, we clarify that while we are not adopting a specific 
automation requirement, we nonetheless believe it is likely that all or 
much of AAR calculation processes will be automated. However, nothing 
in this final rule prevents an individual transmission provider from 
implementing certain portions of the pro forma OATT Attachment M 
requirements manually, should it prefer manual implementation and can 
satisfy the requirements of this final rule.
    363. Finally, some public utility transmission providers may have 
provisions in their existing pro forma OATTs or other document(s) 
subject to the Commission's jurisdiction that the Commission has deemed 
to be consistent with or superior to the pro forma OATT. Where these 
provisions would be modified by this final rule, transmission providers 
must either comply with the requirements adopted in this final rule or 
demonstrate that these previously approved variations continue to be 
consistent with or superior to the pro forma OATT, as modified by this 
final rule.\871\
---------------------------------------------------------------------------

    \871\ See 18 CFR 35.28(c)(1)(vi).
---------------------------------------------------------------------------

V. Information Collection Statement

    364. The information collection (IC) requirements contained in this 
final rule are subject to review by the Office of Management and Budget 
(OMB) under section 3507(d) of the Paperwork Reduction Act of 
1995.\872\ OMB's regulations require approval of certain information 
collection requirements imposed by agency rules.\873\ Respondents 
subject to the filing requirements of this final rule will not be 
penalized for failing to respond to these collections of information 
unless the collections of information display a valid OMB control 
number.
---------------------------------------------------------------------------

    \872\ 44 U.S.C. 3507(d).
    \873\ 5 CFR 1320.11 (2021).
---------------------------------------------------------------------------

    365. This final rule, pursuant to section 206 of the FPA, reforms 
the pro forma OATT and the Commission's regulations to improve the 
accuracy and transparency of electric transmission line ratings used by 
transmission providers. These provisions affect the following 
collections of information: FERC-516H, Pro Forma Open Access 
Transmission Tariff (Control No. 1902-0297); and FERC-725A, Mandatory 
Reliability Standards for the Bulk-Power System (Control No. 1902-
0244).
    366. In the NOPR, the Commission solicited comments on the 
Commission's need for this information, whether the information will 
have practical utility, the accuracy of the burden estimates, ways to 
enhance the quality, utility, and clarity of the information to be 
collected or retained, and any suggested methods for minimizing 
respondents' burden, including the use of automated information 
techniques.
    367. Summary of the Collection of Information in the Final Rule:
    FERC 516H: This final rule amends 18 CFR 35.28(c)(5) to require any 
public

[[Page 2301]]

utility that owns transmission facilities that are not under the public 
utility's control to, consistent with the pro forma OATT required by 18 
CFR 35.28(c)(1), share with the public utility that controls such 
facilities (and its Market Monitoring Unit(s), if applicable):
    (i) Transmission line ratings for each period for which 
transmission line ratings are calculated for such facilities (with 
updated ratings shared each time ratings are calculated); and
    (ii) Written transmission line rating methodologies used to 
calculate the transmission line ratings for such facilities provided 
under subparagraph (i), above.
    Section 35.28(g)(13) of this final rule requires each RTO and ISO 
to establish and maintain systems and procedures necessary to allow any 
public utility whose transmission facilities are under the independent 
control of the ISO or RTO to electronically update transmission line 
ratings for such facilities (for each period for which transmission 
line ratings are calculated) at least hourly, with such data submitted 
by those public utility transmission owners directly into the ISO's or 
RTO's Energy Management System through Supervisory Control and Data 
Acquisition or related systems.
    FERC-725A: Reliability Standard FAC-008-5 is not being revised in 
this proceeding. However, as shown in the burden table below, the 
requirements of this final rule under section 206 of the FPA affect the 
burden for Requirements 2, 3, and 6 in Reliability Standard FAC-008-5.
    368. Title: Pro Forma Open Access Transmission Tariff (FERC-516H) 
and Mandatory Reliability Standards for the Bulk-Power System (FERC-
725A).
    369. Action: Revision of collections of information in accordance 
with Docket No. RM20-16-000.
    370. OMB Control Nos.: 1902-0297 (FERC-516H) and 1902-0244 (FERC-
725A).
    371. Respondents: Transmission owners, transmission service 
providers, generator owners, and RTOs/ISOs.
    372. Frequency of Information Collection: One time and annually.
    373. Necessity of Information: The reforms to the pro forma OATT 
and the Commission's regulations will improve the accuracy and 
transparency of electric transmission line ratings used by transmission 
providers.
    374. Internal Review: The Commission has reviewed the changes and 
has determined that such changes are necessary. These requirements 
conform to the Commission's need for efficient information collection, 
communication, and management within the energy industry. The 
Commission has specific, objective support for the burden estimates 
associated with the information collection requirements.
    375. Our estimates are based on the NERC Compliance Registry as of 
September 3, 2020, which indicates that 78 transmission service 
providers,\874\ 797 generator owners,\875\ and 289 transmission owners 
are registered within the United States and are subject to this 
rulemaking.\876\ There are also six RTOs/ISOs in the United States 
subject to this rulemaking.
---------------------------------------------------------------------------

    \874\ The transmission service provider (TSP) function is a NERC 
registration function which is similar to the transmission provider 
that is referenced in the pro forma OATT. The TSP function is being 
used as a proxy to estimate the number of transmission providers 
that are impacted by this rulemaking.
    \875\ Of the 797 generator owners listed in the September 3, 
2020 NERC Compliance Registry, the Commission estimates that only 
10% of all NERC registered generator owners own facilities between 
the step-up transformer and the point of interconnection. For this 
reason, the Commission estimates that only 80 generator owners are 
affected.
    \876\ The number of entities listed from the NERC Compliance 
Registry reflects the omission of the Texas RE registered entities.
---------------------------------------------------------------------------

    376. Public Reporting Burden: The burden and cost estimates below 
are based on the need for applicable entities to revise documentation, 
already required by the pro forma OATT and the Commission's regulations 
as well as Reliability Standard FAC-008-5, Facility Ratings.\877\
---------------------------------------------------------------------------

    \877\ The burden associated with Reliability Standard FAC-008-5, 
approved by the Commission under section 215 of the FPA, is included 
in the OMB-approved inventory for FERC-725A. Reliability Standard 
FAC-008-5 is not being revised in this proceeding; however, the 
requirements of this final rule under section 206 of the FPA affect 
the burden for three requirements in Reliability Standard FAC-008-5.
---------------------------------------------------------------------------

    377. The Commission estimates that the final rule will affect the 
burden \878\ and cost of FERC-516H and FERC-725A as follows:
---------------------------------------------------------------------------

    \878\ ``Burden'' is the total time, effort, or financial 
resources expended by persons to generate, maintain, retain, or 
disclose or provide information to or for a Federal agency. For 
further explanation of what is included in the information 
collection burden, refer to 5 CFR 1320.3.

                                                     Changes in Final Rule in Docket No. RM20-16-000
--------------------------------------------------------------------------------------------------------------------------------------------------------
               A.                        B.                C.                  D.                        E.                             F.
Area of modification             Number of                   Annual       Annual estimated  Average burden hours & cost   Total estimated burden hours &
                                  respondents.            estimated    number of responses   \879\ per response.           total
                                                          number of  (column B x column C)                                estimated cost
                                                      responses per                                                       (column D x column E)
                                                         respondent
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                      FERC-516H, Pro Forma Open Access Transmission Tariff (Control No. 1902-0297)
--------------------------------------------------------------------------------------------------------------------------------------------------------
For point-to-point transmission  129 (TOs \880\ not               1                    129  1,440 hrs; $120,485.........  185,760 hrs; $15,542,539.
 service requests within ten      in RTOs/ISOs
 days, use AARs in determining    \881\).
 ATC and TTC. (One-Time Burden
 in Year 1).
Where network transmission       160 (to account                  1                    160  1,440 hrs; $120,485.........  230,400 hrs; $19,277,568.
 service is provided, use         for those TOs in
 hourly AARs to determine         RTOs/ISOs that
 curtailment or redispatch of     are not included
 network transmission service.    in the line
 (One-Time Burden in Year 1).     above).
Transmission Providers to        160 (to account                  1                    160  360 hrs; $30,121............  57,600 hrs; $4,819,392.
 implement uniquely determined    for those TOs in
 emergency ratings (One-Time      RTOs/ISOs that
 Burden in Year 1).               are not included
                                  in the line
                                  above).
Implement software and systems   78 (TSPs \882\)...               1                     78  352 hrs; $29,452............  27,456 hrs; $2,297,243.
 to communicate the required
 transmission line ratings with
 relevant parties. (One-Time
 Burden in Year 1).

[[Page 2302]]

 
RTOs/ISOs implement software     6 (RTOs/ISOs).....               1                      6  9,000 hrs; $753,030.........  54,000 hrs; $4,518,180.
 with the ability to
 accommodate AARs in both the
 day-ahead and real-time
 markets on an hourly basis.
 (One-Time Burden in Year 1).
RTOs/ISOs establish the systems  6 (RTOs/ISOs).....               1                      6  1,056 hrs; $88,356..........  6,336 hrs; $530,133.
 and procedures necessary to
 allow transmission owners to
 update line ratings on an
 hourly basis directly into an
 EMS. (One-Time Burden in Year
 1).
Transmission owners update       289 (TOs).........               1                    289  176 hrs; $14,726............  50,864 hrs; $4,255,791.
 forecasts and ratings, and
 share transmission line
 ratings and facility ratings
 methodologies w/transmission
 providers and, if applicable,
 RTOs/ISOs & market monitors
 (Year 1 and Ongoing).
Compliance Filings (One-Time     295 (TOs and (RTOs/              1                    295  160 hrs; $13,387............  47,200 hrs; $3,949,224.
 Burden in Year 1).               ISOs).
                                                    ----------------------------------------------------------------------------------------------------
    Net Subtotal for FERC-516H   ..................  ..............                    373  13,984 hrs; $1,170,041......  429,216 hrs; $50,671,891.
     (Year 1).
                                                    ----------------------------------------------------------------------------------------------------
    Net Subtotal for FERC-516H   ..................  ..............                    289  176 hrs; $14,726............  50,864 hrs; $4,255,791.
     (Ongoing).
--------------------------------------------------------------------------------------------------------------------------------------------------------
                          FERC-725A, Mandatory Reliability Standards for the Bulk-Power System--Reliability Standard FAC-008-5
--------------------------------------------------------------------------------------------------------------------------------------------------------
Review and update facility       369 (TOs & GOs)                  1                    369  40 hrs; $3,347..............  14,760 hrs; $1,234,969.
 ratings methodology,             \883\.
 Requirements R2 and R3. (One-
 Time Burden in Year 1).
Determine facility ratings       369 (TOs & GOs)...               1                    369  8 hrs; $669.................  2,952 hrs; $246,994.
 consistent with methodology,
 Requirement R6. (Burden in
 Year 1 and Ongoing).
                                                    ----------------------------------------------------------------------------------------------------
    Net Subtotal for FERC-725A   ..................  ..............                    369  48 hrs; $4,016..............  17,712 hrs; $1,481,963.
     (Year 1).
                                                    ----------------------------------------------------------------------------------------------------
    Net Subtotal for FERC-725A   ..................  ..............                    369  8 hrs; $669.................  2,952 hrs; $246,994.
     (Ongoing).
--------------------------------------------------------------------------------------------------------------------------------------------------------

    378. The Commission noted in the NOPR that, for purposes of 
estimating burden in the NOPR, the Commission conservatively estimated 
these values based on the maximum number of entities and burden. The 
Commission noted that some entities may, for example, already use AARs 
in their existing operations, in which case the actual burden 
associated with specific reforms associated with the use of AARs would 
be lower than the estimate. The Commission added that, on the other 
hand, changing approaches to facility ratings may require extra testing 
and training for some entities to ensure reliable operations and gain 
familiarity with the approach. In the NOPR, the Commission explained 
that it estimated that the majority of the additional burden associated 
with the NOPR would occur in the first year, and that, once 
established, the ongoing burden would closely approach the existing 
burden of operating the transmission system. The Commission sought 
comment on the estimates in the table provided in the NOPR and the 
assumptions described in the NOPR.
---------------------------------------------------------------------------

    \879\ The hourly cost (for salary plus benefits) uses the 
figures from the Bureau of Labor Statistics (BLS) for three 
positions involved in the reporting and recordkeeping requirements. 
These figures include salary (based on BLS data for May 2019, http://bls.gov/oes/current/naics2_22.htm) and benefits (based on BLS data 
for December 2019; issued March 19, 2020, http://www.bls.gov/news.release/ecec.nr0.htm) and are Manager (Code 11-0000 $97.15/
hour), Electrical Engineer (Code 17-2071 $70.19/hour), and File 
Clerk (Code 43-4071 $34.79/hour). The hourly cost for the reporting 
requirements ($83.67) is an average of the cost of a manager and 
engineer. The hourly cost for recordkeeping requirements uses the 
cost of a file clerk.
    \880\ Transmission Owners. While the AAR reforms in the final 
rule apply to transmission providers, the Commission computes an 
implementation burden based on the number of transmission owners 
because transmission owners typically calculate transmission line 
ratings and are therefore likely to be the entities that update 
computations to determine the effect of changing ambient air 
temperatures on transmission line ratings.
    \881\ Regional Transmission Organizations/Independent System 
Operators.
    \882\ Transmission Service Providers.
    \883\ This number reflects 289 transmission owners and 10% of 
the 797 generator owners (GOs) estimated to own facilities between 
the step-up transformer and the point of interconnection.
---------------------------------------------------------------------------

    379. We have revised the table above to reflect the additional 
burden associated with the additional requirements issued in this final 
rule related to emergency ratings and daytime and nighttime ratings.
    380. We have also revised the table based on comments provided by 
MISO. MISO states that it estimates costs of approximately $200,000 to 
implement AARs for current hour transmission service, and costs to 
implement forecasted AARs in the forward markets and for transmission 
service, such as in

[[Page 2303]]

the day-ahead market, between $500,000 and $750,000.\884\ The 
Commission has conservatively applied this estimate to all of the RTOs/
ISOs. The Commission notes, however, that this is a conservative 
maximum estimate and that some RTOs/ISOs might have pre-existing plans 
to upgrade software in the coming years, which may implement many of 
the same functionalities necessitated by this final rule that are 
captured in these RTO/ISO cost estimates.
---------------------------------------------------------------------------

    \884\ MISO Comments at 32.
---------------------------------------------------------------------------

    381. In this final rule, besides the noted revisions, the 
Commission used the numbers provided in the NOPR.
    382. Interested persons may obtain information on the reporting 
requirements by contacting Ellen Brown, Office of the Executive 
Director, Federal Energy Regulatory Commission, 888 First Street NE, 
Washington, DC 20426 via email ([email protected]) or telephone 
((202) 502-8663).

VI. Environmental Analysis

    383. The Commission is required to prepare an Environmental 
Assessment or an Environmental Impact Statement for any action that may 
have a significant adverse effect on the human environment.\885\ We 
conclude that neither an Environmental Assessment nor an Environmental 
Impact Statement is required for this final rule under section 
380.4(a)(15) of the Commission's regulations, which provides a 
categorical exemption for approval of actions under sections 205 and 
206 of the FPA relating to the filing of schedules containing all rates 
and charges for the transmission or sale of electric energy subject to 
the Commission's jurisdiction, plus the classification, practices, 
contracts, and regulations that affect rates, charges, classification, 
and services.\886\
---------------------------------------------------------------------------

    \885\ Reguls. Implementing the Nat'l Envt'l Pol'y Act, Order No. 
486, 52 FR 47897 (Dec. 17, 1987), FERC Stats. & Regs. Preambles 
1986-1990 ] 30,783 (1987) (cross-referenced at 41 FERC ] 61,284).
    \886\ 18 CFR 380.4(a)(15) (2021).
---------------------------------------------------------------------------

VII. Regulatory Flexibility Act

    384. The Regulatory Flexibility Act of 1980 \887\ generally 
requires a description and analysis of proposed and final rules that 
will have significant economic impact on a substantial number of small 
entities. The Small Business Administration (SBA) sets the threshold 
for what constitutes a small business. The small business size 
standards are provided in 13 CFR 121.201 (2021). Under SBA's size 
standards,\888\ RTOs/ISOs, planning regions, and transmission owners 
all fall under the category of Electric Bulk Power Transmission and 
Control (NAICS code 221121), with a size threshold of 500 employees 
(including the entity and its associates).\889\
---------------------------------------------------------------------------

    \887\ 5 U.S.C. 601-612.
    \888\ 13 CFR 121.201.
    \889\ The RFA definition of ``small entity'' refers to the 
definition provided in the Small Business Act, which defines a 
``small business concern'' as a business that is independently owned 
and operated and that is not dominant in its field of operation. The 
Small Business Administrations' regulations at 13 CFR 121.201 define 
the threshold for a small Electric Bulk Power Transmission and 
Control entity (NAICS code 221121) to be 500 employees. See 5 U.S.C. 
601(3) (citing to Section 3 of the Small Business Act, 15 U.S.C. 
632).
---------------------------------------------------------------------------

    385. The six RTOs/ISOs (SPP, MISO, PJM, ISO-NE, NYISO, and CAISO) 
each employ more than 500 employees and are not considered small.
    386. We estimate that 337 transmission owners and six planning 
authorities are also affected by this final rule. Using the list of 
transmission owners from the NERC Registry (dated September 3, 2020), 
we estimate that approximately 68% of those entities are small 
entities.
    387. We estimate that 80 generator owners own facilities between 
the step-up transformer and the point of interconnection. We estimate 
again that 68% of these are small entities.
    388. We estimate that 78 transmission service providers are 
affected by this final rule. We estimate again that 68% of these are 
small entities.
    389. We estimate additional one-time costs associated with this 
final rule (as shown in the table above) of:
    390. $854,773 for each RTO/ISO (FERC-516H).
    391. $178,719 for each transmission owner (FERC-516H).
    392. $3,347 for each transmission owner (FERC-725A).
    393. $13,387 for each affected generator owner (FERC-516H).
    394. $3,347 for each generator owner (FERC-725A).
    395. $29,452 for each transmission service provider (FERC-516H).
    396. Therefore, the estimated additional one-time cost per entity 
ranges from $16,734 to $854,773.
    397. We estimate that the majority of the additional burden 
associated with this final rule occurs in the first year (as shown in 
the table above), and that, once established, the ongoing burden will 
closely approach the existing burden of operating the transmission 
system.
    398. According to SBA guidance, the determination of significance 
of impact ``should be seen as relative to the size of the business, the 
size of the competitor's business, and the impact the regulation has on 
larger competitors.'' \890\ We do not consider the estimated cost to be 
a significant economic impact. As a result, we certify that this final 
rule will not have a significant economic impact on a substantial 
number of small entities.
---------------------------------------------------------------------------

    \890\ U.S. Small Business Administration, A Guide for Government 
Agencies How to Comply with the Regulatory Flexibility Act, at 18 
(May 2012), https://www.sba.gov/sites/default/files/advocacy/rfaguide_0512_0.pdf.
---------------------------------------------------------------------------

VIII. Document Availability

    399. In addition to publishing the full text of this document in 
the Federal Register, the Commission provides all interested persons an 
opportunity to view and/or print the contents of this document via the 
internet through the Commission's Home Page (http://www.ferc.gov). At 
this time, the Commission has suspended access to the Commission's 
Public Reference Room due to the President's March 13, 2020 
proclamation declaring a National Emergency concerning the Novel 
Coronavirus Disease (COVID-19).
    400. From FERC's Home Page on the internet, this information is 
available on eLibrary. The full text of this document is available on 
eLibrary in PDF and Microsoft Word format for viewing, printing, and/or 
downloading. To access this document in eLibrary, type the docket 
number excluding the last three digits of this document in the docket 
number field.
    401. User assistance is available for eLibrary and the FERC's 
website during normal business hours from FERC Online Support at (202) 
502-6652 (toll free at 1-866-208-3676) or email at 
[email protected], or the Public Reference Room at (202) 502-
8371, TTY (202) 502-8659. Email the Public Reference Room at 
[email protected].

IX. Effective Date and Congressional Notification

    402. This final rule is effective 60 days from the later of the 
date Congress receives the agency notice or the date the rule is 
published in the Federal Register. The Commission has determined, with 
the concurrence of the Administrator of the Office of Information and 
Regulatory Affairs of OMB, that this rule is a ``major rule'' as 
defined in section 351 of the Small Business Regulatory Enforcement 
Fairness Act of 1996.

List of Subjects in 18 CFR Part 35

    Electric power rates, Electric utilities, Reporting and 
recordkeeping requirements.

[[Page 2304]]

    By the Commission. Commissioner Danly is concurring with a 
separate statement attached.

    Commissioner Phillips is not participating.

    Issued: December 16, 2021.
Debbie-Anne A. Reese,
Deputy Secretary.

    In consideration of the foregoing, the Commission amends part 35, 
chapter I, Title 18, Code of Federal Regulations, as follows:

PART 35--FILING OF RATE SCHEDULES AND TARIFFS

0
1. The authority citation for part 35 continues to read as follows:

    Authority:  16 U.S.C. 791a-825r, 2601-2645; 31 U.S.C. 9701; 42 
U.S.C. 7101-7352.

0
2. Amend Sec.  35.28 by adding paragraphs (b)(12) through (16), (c)(5), 
and (g)(13) to read as follows:

Sec.  35.28   Non-discriminatory open access transmission tariff.

* * * * *
    (b) * * *
    (12) Ambient-adjusted rating means a transmission line rating that 
applies to a time period of not greater than one hour; reflects an up-
to-date forecast of ambient air temperature across the time period to 
which the rating applies; reflects the absence of solar heating during 
nighttime periods where the local sunrise/sunset times used to 
determine daytime and nighttime periods are updated at least monthly, 
if not more frequently; and is calculated at least each hour, if not 
more frequently.
    (13) Emergency rating means a transmission line rating that 
reflects operation for a specified, finite period, rather than 
reflecting continuous operation. An emergency rating may assume an 
acceptable loss of equipment life or other physical or safety 
limitations for the equipment involved.
    (14) Dynamic line rating means a transmission line rating that 
applies to a time period of not greater than one hour and reflects up-
to-date forecasts of inputs such as (but not limited to) ambient air 
temperature, wind, solar heating intensity, transmission line tension, 
or transmission line sag.
    (15) Energy Management System (EMS) means a computer control system 
used by electric utility dispatchers to monitor the real-time 
performance of the various elements of an electric system and to 
dispatch, schedule, and/or control generation and transmission 
facilities.
    (16) Supervisory Control and Data Acquisition (SCADA) means a 
computer system that allows an electric system operator to remotely 
monitor and control elements of an electric system.
    (c) * * *
    (5) Any public utility that owns transmission facilities that are 
not under the public utility's control must, consistent with the pro 
forma tariff required by paragraph (c)(1) of this section, share with 
the public utility that controls such facilities (and its Market 
Monitoring Unit(s), if applicable):
    (i) Transmission line ratings for each period for which 
transmission line ratings are calculated for such facilities (with 
updated ratings shared each time ratings are calculated); and
    (ii) Written transmission line rating methodologies used to 
calculate the transmission line ratings for such facilities provided 
under subparagraph (i).
* * * * *
    (g) * * *
    (13) Transmission line ratings. (i) Each Commission-approved 
independent system operator or regional transmission organization must 
establish and maintain systems and procedures necessary to allow any 
public utility whose transmission facilities are under the independent 
control of the independent system operator or regional transmission 
organization to electronically update transmission line ratings for 
such facilities (for each period for which transmission line ratings 
are calculated) at least hourly, with such data submitted by those 
public utility transmission owners directly into the independent system 
operator's or regional transmission organization's EMS through SCADA or 
related systems.
    (ii) [Reserved]

    Note: The following appendix will not be published in the Code 
of Federal Regulations.

Appendix A: Abbreviated Names of Commenters

    The following table contains the abbreviated names of the 
commenters that are used in this final rule.

------------------------------------------------------------------------
      Short name/acronym                       Commenter
------------------------------------------------------------------------
AEP..........................  American Electric Power Company, Inc.
ACORE........................  The American Council on Renewable Energy.
ACPA/SEIA....................  American Clean Power Association (ACPA)
                                and the Solar Energy Industries
                                Association (SEIA).
APS..........................  Arizona Public Service Company.
BPA..........................  Bonneville Power Administration.
CAISO........................  California Independent System Operator
                                Corporation.
CAISO DMM....................  California Independent System Operator
                                Corporation Department of Market
                                Monitoring.
CEA..........................  Canadian Electricity Association.
Certain TDU..................  Certain Transmission Dependent Utilities
                                consist of Alliant Energy Corporate
                                Services, Inc. (Alliant Energy);
                                Consumers Energy Company (Consumers
                                Energy); and DTE Electric Company (DTE
                                Electric).
Clean Energy Parties.........  Clean Energy Parties consist of the
                                Natural Resources Defense Council,
                                Sustainable FERC Project, Conservation
                                Law Foundation, Sierra Club, Western
                                Resource Advocates, Western Grid Group,
                                Clean Grid Alliance, NW Energy
                                Coalition, and Southern Environmental
                                Law Center.
DC Energy....................  DC Energy, LLC.
Dominion.....................  Dominion Energy Services, Inc.
Duke Energy..................  Duke Energy Corporation.
EDFR.........................  EDF Renewables, Inc.
EEI..........................  Edison Electric Institute.
ENEL.........................  ENEL North America.
Entergy......................  Entergy Services, LLC.
EPRI.........................  Electric Power Research Institute.
EPSA.........................  Electric Power Supply Association.
Eversource...................  Eversource Energy Service Company.
Exelon.......................  Exelon Corporation.
IID..........................  Imperial Irrigation District.

[[Page 2305]]

 
Indicated PJM Transmission     Indicated PJM Transmission Owners consist
 Owners.                        of: American Electric Power Service
                                Corporation on behalf of its affiliates,
                                Appalachian Power Company, Indiana
                                Michigan Power Company, Kentucky Power
                                Company, Kingsport Power Company, Ohio
                                Power Company, Wheeling Power Company,
                                AEP Appalachian Transmission Company,
                                Inc., AEP Indiana Michigan Transmission
                                Company, Inc., AEP Kentucky Transmission
                                Company, Inc., AEP Ohio Transmission
                                Company, Inc., and AEP West Virginia
                                Transmission Company, Inc. (collectively
                                ``AEP''); Dominion Energy Services, Inc.
                                on behalf of Virginia Electric and Power
                                Company d/b/a Dominion Energy Virginia;
                                Duke Energy Corporation on behalf of its
                                affiliates Duke Energy Ohio, Inc., Duke
                                Energy Kentucky, Inc., and Duke Energy
                                Business Services LLC; Exelon
                                Corporation; FirstEnergy Service
                                Company, on behalf of its affiliates
                                American Transmission Systems,
                                Incorporated, Jersey Central Power &
                                Light Company, MidAtlantic Interstate
                                Transmission LLC, West Penn Power
                                Company, The Potomac Edison Company,
                                Monongahela Power Company, and Trans-
                                Allegheny Interstate Line Company; PPL
                                Electric Utilities Corporation; and
                                Rockland Electric Company.
Industrial Customer            Industrial Customer Organizations
 Organizations.                 consists of: American Forest & Paper
                                Association (AF&PA), Coalition of MISO
                                Transmission Customers (CMTC),
                                Electricity Consumers Resource Council
                                (ELCON), Industrial Energy Consumers of
                                America (IECA), and the PJM Industrial
                                Customer Coalition (PJMICC).
ISO-NE.......................  ISO New England Inc.
ITC..........................  International Transmission Company d/b/a
                                ITC Transmission, Michigan Electric
                                Transmission Company, LLC, ITC Midwest
                                LLC, and ITC Great Plains, LLC.
LADWP........................  Los Angeles Department of Water and
                                Power.
LineVision...................  LineVision, Inc.
MISO.........................  Midcontinent Independent System Operator,
                                Inc.
MISO Transmission Owners.....  MISO Transmission Owners consist of:
                                Ameren Services Company, as agent for
                                Union Electric Company d/b/a Ameren
                                Missouri, Ameren Illinois Company d/b/a
                                Ameren Illinois, and Ameren Transmission
                                Company of Illinois; American
                                Transmission Company LLC; Big Rivers
                                Electric Corporation; Central Minnesota
                                Municipal Power Agency; City Water,
                                Light & Power (Springfield, IL); Cleco
                                Power LLC; Cooperative Energy; Dairyland
                                Power Cooperative; Duke Energy Business
                                Services, LLC for Duke Energy Indiana,
                                LLC; East Texas Electric Cooperative;
                                Great River Energy; Hoosier Energy Rural
                                Electric Cooperative, Inc.; Indiana
                                Municipal Power Agency; Indianapolis
                                Power & Light Company; International
                                Transmission Company d/b/a ITC
                                Transmission; ITC Midwest LLC; Lafayette
                                Utilities System; Michigan Electric
                                Transmission Company, LLC; MidAmerican
                                Energy Company; Minnesota Power (and its
                                subsidiary Superior Water, L&P);
                                Missouri River Energy Services; Montana-
                                Dakota Utilities Co.; Northern Indiana
                                Public Service Company LLC; Northern
                                States Power Company, a Minnesota
                                corporation, and Northern States Power
                                Company, a Wisconsin corporation,
                                subsidiaries of Xcel Energy Inc.;
                                Northwestern Wisconsin Electric Company;
                                Otter Tail Power Company; Prairie Power
                                Inc.; Southern Illinois Power
                                Cooperative; Southern Indiana Gas &
                                Electric Company (d/b/a Vectren Energy
                                Delivery of Indiana); Southern Minnesota
                                Municipal Power Agency; Wabash Valley
                                Power Association, Inc.; and Wolverine
                                Power Supply Cooperative, Inc.
NERC.........................  North American Electric Reliability
                                Corporation.
New England State Agencies...  New England State Agencies consist of:
                                Connecticut Attorney General William
                                Tong; Massachusetts Attorney General
                                Maura Healey; the Connecticut Department
                                of Energy and Environmental Protection;
                                the Connecticut Office of Consumer
                                Counsel; the Maine Office of the Public
                                Advocate; the New Hampshire Consumer
                                Advocate; Peter F. Neronha, Rhode Island
                                Attorney General; and Thomas J. Donovan,
                                Jr., Attorney General of Vermont.
NRECA/LPPC...................  National Rural Electric Cooperative
                                Association (NRECA) and the Large Public
                                Power Council (LPPC).
NYISO........................  New York Independent System Operator,
                                Inc.
NYTOs........................  The New York Transmission Owners consist
                                of: Central Hudson Gas & Electric
                                Corporation (Central Hudson);
                                Consolidated Edison Company of New York,
                                Inc. (Consolidated Edison); Niagara
                                Mohawk Power Corporation d/b/a National
                                Grid (National Grid); New York Power
                                Authority (NYPA); New York State
                                Electric & Gas Corporation (NYSEG);
                                Orange and Rockland Utilities, Inc.
                                (O&R); Long Island Power Authority
                                (LIPA); and Rochester Gas and Electric
                                Corporation (RG&E).
Ohio FEA.....................  Public Utilities Commission of Ohio's
                                Office of the Ohio Federal Energy
                                Advocate.
OMS..........................  Organization of MISO States.
PacifiCorp...................  PacifiCorp.
PG&E.........................  Pacific Gas and Electric Company.
PJM..........................  PJM Interconnection, L.L.C.
Potomac Economics............  Potomac Economics, LTD.
Prysmian.....................  The Prysmian Group.
R Street Institute...........  R Street Institute.
SCE..........................  Southern California Edison Company.
SDG&E........................  San Diego Gas & Electric Company.
Southern Company.............  Solar Energy Industries Association.
SPP..........................  Southern Company Services, Inc.
SPP MMU......................  Southwest Power Pool, Inc.
Sunflower....................  Sunflower Electric Power Corporation.
Tangibl......................  Tangibl Group, Inc.
TAPS.........................  Transmission Access Policy Study Group.
UDPU.........................  Utah Division of Public Utilities.
Vistra.......................  Vistra Corp.
WAPA.........................  Western Area Power Administration.
WATT.........................  Working for Advanced Transmission
                                Technologies.
WFEC.........................  Western Farmers Electric Cooperative.
------------------------------------------------------------------------

[[Page 2306]]

Appendix B: Pro Forma Open Access Transmission Tariff

ATTACHMENT M

Transmission Line Ratings

General

    The Transmission Provider will implement Transmission Line 
Ratings on the transmission lines over which it provides 
Transmission Service, as provided below.

Definitions

    The following definitions apply for purposes of this Attachment:
    (1) ``Transmission Line Rating'' means the maximum transfer 
capability of a transmission line, computed in accordance with a 
written Transmission Line Rating methodology and consistent with 
Good Utility Practice, considering the technical limitations on 
conductors and relevant transmission equipment (such as thermal flow 
limits), as well as technical limitations of the Transmission System 
(such as system voltage and stability limits). Relevant transmission 
equipment may include, but is not limited to, circuit breakers, line 
traps, and transformers.
    (2) ``Ambient-Adjusted Rating'' (AAR) means a Transmission Line 
Rating that:
    (a) Applies to a time period of not greater than one hour.
    (b) Reflects an up-to-date forecast of ambient air temperature 
across the time period to which the rating applies.
    (c) Reflects the absence of solar heating during nighttime 
periods, where the local sunrise/sunset times used to determine 
daytime and nighttime periods are updated at least monthly, if not 
more frequently.
    (d) Is calculated at least each hour, if not more frequently.
    (3) ``Seasonal Line Rating'' means a Transmission Line Rating 
that:
    (a) Applies to a specified season, where seasons are defined by 
the Transmission Provider to include not fewer than four seasons in 
each year, and to reasonably reflect portions of the year where 
expected high temperatures are relatively consistent.
    (b) Reflects an up-to-date forecast of ambient air temperature 
across the relevant season over which the rating applies.
    (c) Is calculated annually, if not more frequently, for each 
season in the future for which Transmission Service can be 
requested.
    (4) ``Near-Term Transmission Service'' means Transmission 
Service which ends not more than 10 days after the Transmission 
Service request date. When the description of obligations below 
refers to either a request for information about the availability of 
potential Transmission Service (including, but not limited to, a 
request for ATC), or to the posting of ATC or other information 
related to potential service, the date that the information is 
requested or posted will serve as the Transmission Service request 
date. ``Near-Term Transmission Service'' includes any Point-To-Point 
Transmission Service, Network Resource designations, or secondary 
service where the start and end date of the designation or request 
is within the next 10 days.
    (5) ``Emergency Rating'' means a Transmission Line Rating that 
reflects operation for a specified, finite period, rather than 
reflecting continuous operation. An Emergency Rating may assume an 
acceptable loss of equipment life or other physical or safety 
limitations for the equipment involved.

System Reliability

    If the Transmission Provider reasonably determines, consistent 
with Good Utility Practice, that the temporary use of a Transmission 
Line Rating different than would otherwise be required by this 
Attachment is necessary to ensure the safety and reliability of the 
Transmission System, then the Transmission Provider may use such an 
alternate rating. The Transmission Provider must document in its 
database of Transmission Line Ratings and Transmission Line Rating 
methodologies on OASIS or another password-protected website, as 
required by this Attachment, the use of an alternate Transmission 
Line Rating under this paragraph, including the nature of and basis 
for the alternate rating, the date and time that the alternate 
rating was initiated, and (if applicable) the date and time that the 
alternate rating was withdrawn and the standard rating became 
effective again.

Obligations of Transmission Provider

    The Transmission Provider will have the following obligations.
    The Transmission Provider must use AARs as the relevant 
Transmission Line Ratings when performing any of the following 
functions: (1) Evaluating requests for Near-Term Transmission 
Service; (2) responding to requests for information on the 
availability of potential Near-Term Transmission Service (including 
requests for ATC or other information related to potential service); 
or (3) posting ATC or other information related to Near-Term 
Transmission Service to the Transmission Provider's OASIS site or 
another password-protected website.
    The Transmission Provider must use AARs as the relevant 
Transmission Line Ratings when determining whether to curtail (under 
section 13.6) Firm Point-To-Point Transmission Service or when 
determining whether to curtail and/or interrupt (under section 14.7) 
Non-Firm Point-To-Point Transmission Service if such curtailment 
and/or interruption is both necessary because of issues related to 
flow limits on transmission lines and anticipated to occur (start 
and end) within 10 days of such determination. For determining 
whether to curtail or interrupt Point-To-Point Transmission Service 
in other situations, the Transmission Provider must use Seasonal 
Line Ratings as the relevant Transmission Line Ratings.
    The Transmission Provider must use AARs as the relevant 
Transmission Line Ratings when determining whether to curtail (under 
section 33) or redispatch (under sections 30.5 and/or 33) Network 
Integration Transmission Service or secondary service if such 
curtailment or redispatch is both necessary because of issues 
related to flow limits on transmission lines and anticipated to 
occur (start and end) within 10 days of such determination. For 
determining the necessity of curtailment or redispatch of Network 
Integration Transmission Service or secondary service in other 
situations, the Transmission Provider must use Seasonal Line Ratings 
as the relevant Transmission Line Ratings.
    The Transmission Provider must use Seasonal Line Ratings as the 
relevant Transmission Line Ratings when evaluating requests for and 
whether to curtail, interrupt, or redispatch any Transmission 
Service not otherwise covered above in this section (including, but 
not limited to, requests for non-Near-Term Transmission Service or 
requests to designate or change the designation of Network Resources 
or Network Load), when developing any ATC or other information 
posted or provided to potential customers related to such services. 
The Transmission Provider must use Seasonal Line Ratings as a 
recourse rating in the event that an AAR otherwise required to be 
used under this Attachment is unavailable.
    The Transmission Provider must use uniquely determined Emergency 
Ratings for contingency analysis in the operations horizon and in 
post-contingency simulations of constraints. Such uniquely 
determined Emergency Ratings must also include separate AAR 
calculations for each Emergency Rating duration used.
    In developing forecasts of ambient air temperature for AARs and 
Seasonal Line Ratings, the Transmission Provider must develop such 
forecasts consistent with Good Utility Practice and on a non-
discriminatory basis.
    Postings to OASIS or another password-protected website: The 
Transmission Provider must maintain on the password-protected 
section of its OASIS page or on another password-protected website a 
database of Transmission Line Ratings and Transmission Line Rating 
methodologies. The database must include a full record of all 
Transmission Line Ratings, both as used in real-time operations, and 
as used for all future periods for which Transmission Service is 
offered. Any postings of temporary alternate Transmission Line 
Ratings or exceptions used under the System Reliability section 
above or the Exceptions section below, respectively, are considered 
part of the database. The database must include records of which 
Transmission Line Ratings and Transmission Line Rating methodologies 
were in effect at which times over at least the previous five years, 
including records of which temporary alternate Transmission Line 
Ratings or exceptions were in effect at which times during the 
previous five years. Each record in the database must indicate which 
transmission line the record applies to, and the date and time the 
record was entered into the database. The database must be 
maintained such that users can view, download, and query data in 
standard formats, using standard protocols.
    Sharing with Transmission Providers: The Transmission Provider 
must share, upon request by any Transmission Provider and in a 
timely manner, the following information:
    (1) Transmission Line Ratings for each period for which 
Transmission Line Ratings

[[Page 2307]]

are calculated, with updated ratings shared each time Transmission 
Line Ratings are calculated, and
    (2) Written Transmission Line Rating methodologies used to 
calculate the Transmission Line Ratings in (1) above.
    Exceptions: Where the Transmission Provider determines, 
consistent with Good Utility Practice, that the Transmission Line 
Rating of a transmission line is not affected by ambient air 
temperature or solar heating, the Transmission Provider may use a 
Transmission Line Rating for that transmission line that is not an 
AAR or Seasonal Line Rating. Examples of such a transmission line 
may include (but are not limited to): (1) A transmission line for 
which the technical transfer capability of the limiting conductors 
and/or limiting transmission equipment is not dependent on ambient 
air temperature or solar heating; or (2) a transmission line whose 
transfer capability is limited by a Transmission System limit (such 
as a system voltage or stability limit) which is not dependent on 
ambient air temperature or solar heating. The Transmission Provider 
must document in its database of Transmission Line Ratings and 
Transmission Line Rating methodologies on OASIS or another password-
protected website any exceptions to the requirements contained in 
this Attachment initiated under this paragraph, including the nature 
of and basis for each exception, the date(s) and time(s) that the 
exception was initiated, and (if applicable) the date(s) and time(s) 
that each exception was withdrawn and the standard rating became 
effective again. If the technical basis for an exception under this 
paragraph changes, then the Transmission Provider must update the 
relevant Transmission Line Rating(s) in a timely manner. The 
Transmission Provider must reevaluate any exceptions taken under 
this paragraph at least every five years.

FEDERAL ENERGY REGULATORY COMMISSION

Managing Transmission Line Ratings
Docket No. RM20-16-000

(Issued December 16, 2021)

DANLY, Commissioner, concurring:

    1. I concur with the issuance of this final rule because I agree 
that the record in this proceeding supports a finding that current 
transmission rates are unjust and unreasonable because line rating 
information is often inaccurate.\1\ The rates customers pay to 
support transmission are distorted because the ratings that purport 
to represent the true operating characteristics of the transmission 
system are distorted. The voluminous record evidence in this 
proceeding is sufficient to support a Federal Power Act section 206 
action to remedy unjust and unreasonable rates.\2\ The record also 
is sufficient to support the replacement rates we order in this 
rule.
---------------------------------------------------------------------------

    \1\ Managing Transmission Line Ratings, 177 FERC ] 61,179 at P 
29 (2021).
    \2\ 16 U.S.C. 824e.
---------------------------------------------------------------------------

    2. Of course, we cannot act pursuant to section 206 without 
substantial record evidence that the existing rate is unjust and 
unreasonable and further record support for a replacement rate. We 
cannot impose a requirement for dynamic line ratings, for example, 
because we do not have the record support to do so at this time.\3\ 
Action cannot be taken under section 206 merely because a potential 
reform is a good idea or because a contemplated policy might yield 
greater efficiencies.
---------------------------------------------------------------------------

    \3\ See Managing Transmission Line Ratings, 177 FERC ] 61,179 at 
P 36 (declining to require dynamic line ratings).
---------------------------------------------------------------------------

    3. Here, I am persuaded that we have sufficient record evidence 
to require ambient-adjusted ratings (AAR) on all transmission lines 
because the record shows the existing paradigm significantly 
distorts efficient use of the transmission system.\4\ In addition, 
AAR is a just and reasonable replacement rate because the record 
evidence shows the additional costs are incremental and will provide 
significant benefits.
---------------------------------------------------------------------------

    \4\ Id. at P 83.
---------------------------------------------------------------------------

    4. In this case, the requirements of both steps of section 206 
have been satisfied. As a Commission, we must ensure that every 
action taken under section 206 fully meets these burdens and I will 
apply the same rigorous analysis to every future section 206 
proposal to improve the transmission system.
    For these reasons, I respectfully concur.

James P. Danly,

Commissioner.

[FR Doc. 2021-27735 Filed 1-12-22; 8:45 am]
BILLING CODE 6717-01-P