From: Simmons, Chuck [mailto:Chuck.Simmons@pgnmail.com] 

Sent: Friday, September 23, 2011 3:06 PM 

To: 'richard.parker@law.uconn.edu' 

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Subject: General Comments to the Liquid-Immersed and Medium Voltage Dry-Type Distribution 

Transformers Negotiated Rulemaking Working Group 

Mr. Parker: 

Following up on your request that members of the Liquid-Immersed and Medium Voltage Dry-Type 

Distribution Transformers Negotiated Rulemaking Working Group submit questions and concerns 

relative to our discussions. 

1) Progress Energy does not currently use A and B factors for distribution transformer purchases 

that are covered by the DOE Final Ruling efficiency requirements. We performed an evaluation 

of what the cost would be and determined that the payback would be way out in the 40-50 year 

range for most designs. We expected this as the payback for the DOE requirements was in the 

30-40 year range. Comparing pre-2010 designs with those that fall under the Final Ruling 

requirements (with compliance date of 1/1/2010), we have not seen any significant deviation in 

the ratio of No Load to Load loss values. But since the use of “A” and “B” factors is no longer a 

viable choice for many utilities or other users due to the potential cost increases, there could be 

drastic inefficiencies with future distribution transformer designs that only have to meet a single 

efficiency value. By using A and B factors (as previously done by a large number of distribution 

transformer buyers), a weighting could be assigned to No Load and Load losses depending on a 

utilities cost of capital, cost of generation, transformer loading factor, cost of transmission, and 

many other important factors to utilities required to determine the relative economic value of 

various transformer designs. Since both No Load and Load losses cost users, Users are very 

interested in ensuring that a method is arrived at that gives the same consideration as the A and B 

factors did in the past and maintains reasonable costs for customers. 

2) I think the average load estimate of 45% used in the analysis is incorrect. Progress 

Energy Carolinas reviewed system peak data from this past summer (2011) and 

determined that during the system peak, the average load realized by distribution 

transformers was 34% of the available nameplate kVA of all distribution transformers on 

the system. Based on discussions with other utilities, the DOE should model distribution 

transformers being loaded between 25-35% of the rated nameplate kVA value as this 

appears to be typical for most utilities. As some of the transformer vendors indicated 
during the subcommittee’s previous (first meeting), using the 45% average load factor 

forces distribution transformer designs that are oversized which cost more money to build 

and creates issues with material availability. Accurate transformer loading values should 

be confirmed and used in the modeling process. 

3) I would like to re-emphasize comments from Wes Patterson and others on the most recent 

analyses. The subcommittee should be provided with information as to the rationale used by both 

Navigant and Lawrence Berkley Laboratories (LBL) for determining the efficiency levels arrived 

at in Tables 1.1, 1.2 and 1.3 of the “Analytical Results In Support of Stakeholder Negotiations on 

Amended Energy...” dated August 23, 2011. Additionally, both consultants should prepare and 

provide replies to all questions related to the designs used and referenced in this document. Many 

valid questions have been submitted by subcommittee members and need to be addressed such 

that we can ascertain the validity of the analyses to date and what changes may be necessary in 

the future. 

4) The DOE needs to require completely separate designs for each type of design (1-phase 

rectangular, 1-phase overhead, 3-phase padmount, 3-phase network, and 3-phase vault type 

transformers) as well as corroborate these designs with vendors as the program used by the DOE 

consultants does not appear to line up with what the vendors designs reflect. Any lines that result 

from interpolation should also be verified with input from vendors. The scaling factors don’t 

appear to be very accurate. Additionally, designs need to be created for both network and vault 

type transformers as these are different from 3-phase rectangular type designs (scaling from 3-

phase rectangular designs isn’t acceptable for networks and vault type designs). 

5) The DOE needs to investigate and revise, as needed, market estimates as reflected in Wes 

Patterson’s comments on the most commonly purchased distribution transformers. 

6) Some items that DOE should take into account with network type transformers are; a) the 

requirement that tanks be constructed of copper-bearing steel, b) availability issues with network 

protectors and/or switches, c) sensitivity to dimensions since these units need to fit into an 

existing vault / hole. 

7) Some items that DOE should take into account with vault type transformers are; a) Requirement 

of stainless steel tank and external parts (typically 304L), b) Requirement for a high fire-point 

fluid (which is typically on the order of 11-15 $/gallon, c) sensitivity to dimensions since these 

units need to fit into an existing vault / hole. 

8) The percentage of distribution transformer buyers that actually evaluate transformer purchases 

with A and B factors needs to be confirmed. Some of the data provided by the DOE’s consultants 

has been questioned and needs to be verified. 

9) The average life of a transformer should be confirmed. The DOE analysis was based on 32 years 

(this is what Navigant used) and that lifetime is not accurate based on the experience of most 

utilities. The C57.91 Loading Guide average life is approximately 21 years. I believe 21 years to 

be more accurate. Sensitivity analysis should be performed with the transformer life being 

between 20-40 years. 

10) Core steel availability is a significant concern for both manufacturers and utilities. Prior to the 

current economic slump, core steel prices were at their highest levels ever due to limited supply 

and record demand. Transformer manufacturers were allotted a certain amount of core steel, 
which created availability issues. Since there has not been a significant increase in the 

availability of core steel (either grain oriented silicon or amorphous), so there should be a great 

effort expended to fully consider all implications in core steel requirements. Under no 

circumstances should any efficiency standard be set that limits the number of core steel suppliers 

to any number less the current three. The last thing we need are efficiency requirements result in 

only one core steel supplier being a sole source. The core steel required by the DOE’s efficiency 

requirements infringes upon those of medium and large power transformers, such that if demand 

of either increases (which history tells us both will), there will be issues with adequate supply. 

11) Does the DOE have information regarding the expected life of amorphous core steel? It appears 

that amorphous core steel was used in distribution transformers for a period of time and then 

usage slowed down (at least in distribution transformers) quite a bit. Progress Energy, as do most 

utilities, hope that amorphous core steel proves to be as good, if not better, than grain oriented 

core steel, but that needs to be substantiated first. 

Regards, 

Chuck Simmons, P.E. 

Distribution Standards 

Progress Energy 

14 18 Mechanical Boulevard 

Garner, NC 27529 

Phone: 919-662-6033