Proposed Changes In The NESC

George Bagnall, Director, Electric Staff Division, RUS

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National Electrical Safety Code Importance

The National Electrical Safety Code (NESC) is an extremely important document to

electric utilities for many reasons. The NESC is the paramount document that most

state and local authorities look to for mandating how operators of electric and

telecommunications utilities are to install, operate, and maintain their facilities. In

addition, from years of experience, NESC compliant electric facilities have proven to

provide a reliably safer environment for the general public and for utility employees.

Utility operators must also keep in mind that the NESC is the most authoritative

referenced document used in courtroom dramas where electric utilities sometimes find

themselves defending claims of causing harm to people and animals; and proof of

historical, continuous, NESC compliance provides utilities one of the strongest defenses.

NESC Subcommittee Composition

The Institute of Electrical and Electronic Engineers (IEEE) is the NESC Secretariat and

entity responsible for development and revision of the NESC. IEEE maintains an

Executive Committee and seven subcommittees to oversee this revision responsibility.

Subcommittee membership includes a balanced representation of individuals from

electric, telecommunications and other utilities, labor unions, various associated industry

groups, government agencies, and industry experts.

Committee/Subcommittee* Committee Responsibility*

Accredited Standards C2 Final IEEE Approval of NESC; Comments received from

letter ballots and public.

Subcommittee 1 Purpose, Scope, Application, Definitions, and References

Sections 1, 2, and 3.

Subcommittee 2 Grounding Methods

Section 9

Subcommittee 3 Electric Supply Stations

Sections 10, 11, 12, 13, 14, 15, 16, 17, 18, and 19

Subcommittee 4 Overhead Lines - Clearances

Sections 20, 21, 22, and 23

Subcommittee 5 Overhead Lines - Strength and Loading

Sections 24, 25, 26, and 27

Subcommittee 7 Underground Lines

Sections 30, 31, 32, 33, 34, 35, 36, 37, 38, and 39

Subcommittee 8 Work Rules

Sections 40, 41, 42, 43, and 44

* There is no Subcommittee 6 and there are no Sections 4, 5, 6, 7, 8, 28, and 29.
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The Rural Utilities Service (RUS), Electric Staff Division (ESD), maintains membership

on NESC Subcommittees to assure the NESC includes a perspective of the concerns

and reality of installing and operating electric facilities in rural America.

The following details RUS subcommittee membership:

RUS NESC Committee and Subcommittee Membership

Name ESD Job Title Committee

George J. Bagnall Director, ESD NESC (Main) Committee

Harvey Bowles Chair, Technical Standards

Committee "A" (Electric)

Subcommittee 2

James L. Bohlk Electrical Engineer Subcommittee 4

Donald G. Heald Structural Engineer Subcommittee 5

Trung Hiu Electrical Engineer Subcommittee 7

NESC Revision Activities

At the present time, all seven subcommittees are actively engaged in developing the

Year 2002 edition of the NESC. The first step in revision involves entertaining

submissions from the public of proposed changes to the 1997 edition of the code. (The

NESC calls proposed changes "Change Proposals" or CPs and assigns CPs

consecutive numbers as the CPs are received by mail from the public). For the current

NESC revision cycle, all CPs had to be submitted to IEEE by July, 1998. The

Subcommittees subsequently met in October, 1998, and considered all CPs submitted

by the public. Actions taken on the CPs by the Subcommittees were published in the

September 1, 1999, publication, "NESC Preprint 2002 Proposals." Interested parties

have until May 1, 2000, to provide comments or suggestions on the actions taken by the

Subcommittees. The Subcommittees will meet again in October, 2000, to discuss and

consider the public comments received in response to the actions taken by

subcommittees. On January 15, 2001, the final recommended version of the 2002

NESC will be sent to the NESC Accredited Standards C2 Committee for letter ballot and

to the American National Standards Institute (ANSI) for concurrent public review.

Publication of the final 2002 NESC is expected in August, 2001.

For the revision process to work effectively, it is crucial that all interested parties

participate by:

(1) Submitting CPs that will help improve the content of the NESC1,

(2) Obtaining and reviewing the NESC Subcommittee CP resolutions

included in the Preprint 2002 Proposals, and

 

*

1

 CPs for the 2007 NESC will be due sometime in July, 2003.
3

(3) Submitting comments on the NESC Subcommittees' recommendations

and actions with respect to submitted CPs2.

RUS highly recommends that RUS borrowers, their consulting engineers, suppliers, and

others associated with the rural electric utility industry, become involved in this

three-step process.

Order Your Copy of the Preprint

It is too late to submit CPs for the 2002 revision cycle but it is not too late to review the

subcommittees' actions taken on CPs and to provide comments on these actions.

Preprint 2002 Proposals can be ordered by telephoning IEEE at: 1 (800) 678-4333.

Send Your Comments

Comments, post marked no later than May 1, 2000, must be in writing on the form

provided in the Preprint 2002 Proposals. A copy of this form is shown on Page 26 of this

paper. IEEE also requires that a separate form be used for each comment. Comments

must be sent to:

Secretary, National Electrical Safety Code

IEEE Standards Activities

445 Hoes Lane, P.O. Box 1331

Piscataway, NJ 08855-1331

Change Proposals of Interest to RUS Electric Borrowers

The balance of this paper presents, in order of appearance in the Preprint 2002 Proposal

publication, Subcommittee actions on CPs that may be of interest to RUS electric

borrowers. (The pages on which the CPs appear in the Preprint are shown in

parenthesis after the CP number). Where text of Subcommittee actions is quoted in this

paper, proposed new text additions are shown in underlined italic fonts with existing text

shown in italic fonts. Only CPs that would result in changes to the NESC are presented

here. Note, however that the Subcommittees acted on many CPs in such a manner that

the NESC would not be revised but these Subcommittee determinations are as

meaningful and useful as those actions that result in code revisions because the

Subcommittee explanations provide excellent insight and background information about

the NESC. RUS encourages all borrowers' engineers and their consultants to obtain a

copy of the Preprint 2002 Proposals.

 

*

2

 Comments on the Subcommittees CP actions for the 2002 NESC are due by May 1, 2000.
4

Remember that the proposals presented here may not survive the entire process

of revision so provisions could be amended or they could be completely removed

M WARNING M

from consideration and not appear in the 2002 edition of the NESC. Readers

should not count on or use any of the proposed changes included in this paper or

the Preprint 2002 Proposals publication for utility construction to be completed in

2002. Only the officially published 2002 version of the NESC should be used.

Change Proposals

CP 2205 (Page 4)

Subject: Safe Clearances provided in Parts 1, 2, and 4

Proposal: This CP advised that there are inconsistencies in the ac and dc safe

clearances that need to be corrected in the following NESC Parts:

l Part 1, "Rules for the Installation and Maintenance of Electric Supply Stations

and Equipment," (Related to Clearance Guard to Live Parts),

l Part 2, "Safety Rules for the Installation and Maintenance of Overhead Electric

Supply and Communication Lines," (Related to Electrical Components of

Clearance), and

l Part 4, "Rules for the Operation of Electric Supply and Communications Lines

and Equipment." (Related to Work Rules - Minimum Approach Distance).

Subcommittee Actions: The revisions required by this CP fall under the responsibility

of Subcommittees 1, 3, 4, and 8. Subcommittee 1 agreed to form Working Group 1.8

which is to either define a common basis or source for clearances recommended in

Parts 1, Part 2, and Part 4, or identify the appropriate differences in the various

clearances. Subcommittees 3 and 4 both agreed to the establishment of a working

group to resolve the issue. Subcommittee 4 rejected the proposal citing that it did not

see a clear need to change the clearance values in Part 2. The Preprint 2002 Proposals

does not definitively address the resolution or status of these subcommittee actions,

making it difficult to develop and submit public comments.

CP 2140 (Page 14)

Subject: Rule 011 (NESC Scope) and recognizing street and area lighting in NESC

Proposal: Revise NESC Rule 011 (Scope) to include in the NESC scope that the NESC

includes provisions for street lights and area lights that are under the control of utilities or
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other qualified persons while provisions for other types of facilities are found in the

National Electric Code (NEC).

Subcommittee Action: Subcommittee 1 acted by proposing to change Rule 011 by

adding new language that states the NESC covers utility facilities and functions up to the

service point and that the NEC covers utilization wiring requirements beyond the service

point.

CP 2136 (Page 15)

Subject: Rule 013 (NESC Application) and experimental construction and methods of

installation

Proposal: Revise Rule 013A2 to add to the provisions for experimental installations

such that, in addition to requiring qualified supervision, that equivalent safety be

provided and that all affected parties of joint use construction agree to allow the

experimental installation.

Subcommittee Action: Subcommittee 1 agreed in part to the CP request by proposing

to revise Rule 013A2 as proposed in CP 2136 except for the requirement related to joint

use facilities. Subcommittee 1 revised the proposed language such that on joint use

facilities, all affected parties be notified rather than requiring all affected parties to agree

to allow the experimental construction.

CP 2312 (Page 16)

Subject: Rule 015 (NESC Intent) and exceptions to NESC Rules

Proposal: Add a new Rule 015G that states that exceptions to a rule have the same

force and effect required or allowed by the rule to which the exception applies.

Subcommittee Action: Subcommittee 1 is proposing to rearrange Rule 015 and include

as "D" the exact language requested in the CP.

CP 2370 (Page 27)

Subject: Section 2 (Definitions) and inclusion of a definition for Fiber-reinforced

composite structure

Proposal: Include a definition for fiber-reinforced composite structure to read: "Fiberreinforced thermoset or thermoplastic resin structure and structural components.

Subcommittee Action: Subcommittee 1 is proposing to add the following definition:

Fiber-reinforced composite structure and components. Fiber-reinforced

thermoset or thermoplastic resin structure and structural components.
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CP 2383 (Page 28)

Subject: Section 2 (Definitions) and inclusion of various definitions related to grounding

Proposal: Include definitions for ungrounded system, grounded system, unigrounded or

single grounded, impedance grounded, multigrounded system, shield wire/conductor

and neutral conductor. Language for all requested definitions was provided in CP 2383.

Subcommittee Action: Subcommittee 1 proposed that the request be referred to

Working Group 2.1. Working Group 2.1 met and considered each of the definitions

proposed. The Working Group proposed definitions for "ungrounded system,"

"multigrounded/multiple grounded system," "single grounded/unigrounded," neutral

conductor," and "shield wire/conductor." Of particular interest was the proposed

addition of the definition for "multigrounded/multiple grounded system. This definition

includes a statement that a multigrounded or multiple grounded system may not be

effectively grounded.

CP 2162 (Page 33)

Subject: Section 2 (Definitions) and Definition of "Qualified"

Proposal: Replace the present definition of "qualified" with the one included in the

proposed CP.

Subcommittee Action: Subcommittee 1 proposed its own definition to read as follows:

"qualified. Having been trained in and having demonstrated adequate knowledge of

the installation, construction, or operation of lines and equipment and the

hazards involved, including identification of and exposure to electric supply

and communication apparatus in or near the workplace. An employee who

is undergoing on-the-job training and who, in the course of such training,

has demonstrated an ability to perform duties safely at his or her level of

training, and who is under the direct supervision of a qualified person, is

considered to be a qualified person for the performance of those duties."

CP 2314 (Page 50)

Subject: Rule 93A (Grounding Conductor and Means of Connection – Composition of

Grounding Conductors) and allowing equipment tanks as part of conduction path

Proposal: Include in Rule 93A the provision that the case of metallic equipment is

allowed to be part of the grounding conduction path.

Subcommittee Action: Subcommittee 2 proposed to revise the last sentence of Rule

093A as follows:

Metallic electrical equipment cases or the structural metal frame of a building or

structure may serve as part of a grounding conductor to an acceptable grounding

electrode.
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CP 2244 (Page 58)

Subject: Rule 94B2b (Driven Rods) and alternative driven rods

Proposal: Include an exception to Rule 094B2b to read as follows:

Exception 1: Other dimensions or configurations may be used if their suitability is

supported by a qualified engineering study.

Subcommittee Action: Subcommittee 2 accepted this proposal as submitted. The

supporting documentation submitted with the proposal includes a sample of the type of

engineering study intended for consideration when implementing this proposed new

exception.

CP 2382 (Page 66)

Subject: Rules 96C (Ground Resistance Requirements – Multi-Grounded Systems),

97A and B (Separation of Grounding Conductors) and shield wires used for lightning

protection

Proposal: Working Group 2.1 proposed to add a "Recommendation" to Rule 96C (Multigrounded systems) that reads as follows:

Recommendation: This Rule may be applied to shield wire(s) used as lightning

protection conductor(s), which is grounded at the source and that meets the

multigounding requirements of this Rule.

Working Group 2.1 also proposed to revise Rule 97A by adding shield wires of power

circuits as an additional class of the classes included in the Rule. The Working

Group 2.1 proposal also included changing Rule 97B such that shield wires of power

circuits would be added as a third equipment class to which a single bonding conductor

(bonded to all [of the three] equipment classes cited in the Rule) would be allowed for

grounding the equipment.

Subcommittee Action: Subcommittee 2 accepted the Working Group 2.1 proposal as

submitted.

CP 2264 (Page 83)

Subject: Rule 110B1 (Protective Arrangements in Supply Stations – Rooms and

Spaces) and addition of a note re not preventing use of wood poles

Proposal: Add to Rule 110B1 wording that advises it is not intended that this Rule

prevents the use of wood poles in equipment rooms.

Subcommittee Action: Subcommittee 2 proposed revision of Rule 110B1 as follows:
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1. Construction

They shall be as much as practical noncombustible.

Note: This Rule is not intended to prevent wood poles from being used to

support conductors or equipment in electric supply stations.

CP 2211 (Page 107)

Subject: Rule 214A2 (Overhead – Inspection and tests of Lines and Equipment) and

allowing inspections while performing other duties

Proposal: Include language in Rule 214A2 that allows inspections to be performed while

performing other duties.

Subcommittee Action: Subcommittee 4 accepted a modified version of the proposal

by adding the following sentence to Rule214A2:

Inspections may be performed in a separate operation or while performing other

duties.

CP 2388 (Page 121)

Subject: Rule 230A (Overhead – Clearances and General Applications) and the

application of NESC clearances

Proposal: Subcommittee 4 proposed the following revision of Rule 230A to help

alleviate confusion of NESC clearance requirements:

A. Development and Application of Clearances

This section covers clearances, including climbing spaces, involving

overhead supply and communication lines. Rules 232 and 234 contain

tables of required clearances from overhead facilities to land and water

areas and to structures used, occupied, or worked upon by members of

the public. These clearances were developed from the methodology,

reference dimensions, and clearance building blocks shown in

Appendix A. This accepted good practice is based upon the results of

almost a century of application of NESC clearances in the field.

The clearances specified in Section 23 apply to the vast majority of

overhead installations. It is exceptionally rare that local conditions are not

specified in these Rules. However, the clearances specified in Section 23

do not cover unusual activities or use of oversized equipment, such as

may occur at construction sites. If such a circumstance occurs where the

known dimensions of conflicting activity exceed the Reference

Dimensions of Table A-2a or Table A-2b, Rule 012C requires accepted

good practice to be met. Although, Appendix A is not a mandatory

section of the NESC, Rule 012C may be met by adding the applicable

M&E values from Table A-1 to the known dimensions of conflicting activity

to develop the clearance that is appropriate for the unspecified condition.
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This methodology may be used to determine applicable clearances for

unusual situations.

Note: The NESC recognizes that activities of construction personnel and

other workers in close proximity to existing supply lines are governed by

Occupational Safety and Health Administration (OSHA) regulations

contained in 29 Code of Federal Regulations Parts 1910 and 1926.

These regulations require construction personnel and other workers to

maintain appropriate working clearances of personnel, tools, and

equipment from supply lines. Also, most states have similar requirements

applicable to individuals working in close proximity to supply lines.

Subcommittee Action: Subcommittee 4 accepted the proposal as presented.

CP 2256 (Page 136)

Subject: Rule 231B1 (Overhead – Clearances of Supporting Structures from Other

Objects – From Streets, Roads, and Highways) and recognition of "Swale-type" curbing

Proposal: This proposal included a revision to Rule 231B that would add an alternative

to existing text requiring supporting structures, support arms or equipment attached

thereto to be located behind the curb. The proposal also requested removal of the last

sentence of the rule pertaining to the minimum distance 150 mm (6 in) because the

requirement could not be readily applied to “Swale-type” curbs.

Subcommittee Action: Subcommittee 4 accepted the proposal in principle by adding

the following sentence to the end of the rule:

For paved or concrete swale-type curbs, such facilities shall be located behind

the curb.

CPs 2325 (Page 139) and 2326 (Page 139)

Subject: Rule 232B2 and 3 (Overhead – Clearances of Wires, Conductors, Cables, and

Equipment Above Ground, Roadway, Rail, or Water Surfaces) and clearances to

unguarded rigid live parts of equipment and equipment cases

Proposal: Both CPs requested that "water" be specifically added as a surface over

which clearances are specified in the two Rules.

Subcommittee Action: Subcommittee 4 accepted both proposals as presented.
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CP 2327 (Page 149)

Subject: Table 232-1 (both metric and English unit tables) [Vertical Clearance of Wires,

Conductors, Cables, and Equipment Above Ground, Roadway, Rail, or Water Surfaces]

and correction of redundancies

Proposal: This proposal suggested implementing the following revisions to both the

metric and English unit version of Table 232-1:

(1) Adding "not subject to truck traffic" to the wording for Footnote 13 for the

table to clear up a redundancy and misuse created during previous revisions,

(2) Deleting Footnote 13 from Table 232-1, Row 9, category because it does not

apply, and

(3) Adding Footnote 21 to the Row 3 category of Table 232-1 to help clarify the

truck height definition as it relates to the category.

Subcommittee Action: Subcommittee 4 accepted the proposal as submitted.

CP 2143 (Page 167)

Subject: Rule 234B1 (Clearances of Wires, Conductors and Cables From Other

Supporting Structures) Exception and “effectively grounded”

Proposal: This proposal suggested adding the wording "effectively grounded" before

"guys and messengers" in the exception which allows a clearance of 3 ft. (0.9 m), in lieu

of the Rule requirement of 4 ft. (1.2 m). The submitter stated that the Rule was originally

written with the intent that the exception pertains only to effectively grounded guys and

messengers and, thus, the addition is needed for clarity.

Subcommittee Action: Subcommittee 4 accepted the proposal as submitted.

CPs 2114 (Page 171) and 2144 (Page 172)

Subject: Rules 234C3d and d1 (Clearances of Wires, Conductors, Cables, and Rigid

Live Parts from Buildings, Signs, Billboards, Chimneys, Radio and Television Antennas,

Tanks, and Other Installations Except Bridges), and revision of the Exception related to

service drop clearances

Proposal: These proposals suggest substantive revision of service drop clearances

from roofs or balconies that would change a current 3 ft. (0.9 m) requirement to 18 in.

(0.5), under specified installation conditions. The proposals also include adding wording

to specify that the service drop conductors must comply with the covered conductors

provisions of Rule 230D so that it is explicitly understood that bare conductors are not

allowed.

Subcommittee Action: Subcommittee 4 accepted the proposals as submitted.
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CP 2146 (Page 183)

Subject: Rule 234F1 (Clearances of Wires, Conductors, Cables, and Rigid Live Parts

from Grain Bins) and probe ports at grain bin installations

Proposal: This proposal adds an Exception to Rule 234F1 to require clearances near

the probe ports of grain bins to be not less than the clearances of Rule 234C. The

revision intent was to make certain that supply circuits are not in the way of farm

personnel or oriented such that the conductors could fall and dangerously electrify any

part of the bin installation.

Subcommittee Action: Subcommittee 4 accepted a modified version of the CP which

essentially changes the requirements for service drops installed near grain bins with the

concerns of the proposer considered.

CP 2147 (Page 187)

Subject: Rule 235C (Clearances for Wires, Conductors, or Cables Carried on the Same

Supporting Structure – Vertical Clearance Between Line Conductors) and using the word

“conductors” to mean “wires and cables”

Proposal: This proposal asked that the following sentence be added to Rule 235C: "For

the purposes of this Rule, the term conductors shall include wires and cables, unless

otherwise specified.

Subcommittee Action: Subcommittee 4 accepted the proposal in principal by making

the substitution "line wires, conductors and cables" wherever "conductors" appears in

Rules 235C2a(1) and b(1). As a result of this CP, Subcommittee 4 also established a

special Working Group which reviewed all Rules in Section 23 for the

"conductors"/"wires, cables, lines, etc.," concern. The Working Group prepared a

version of Section 23 which includes the Working Group’s recommended choice of

terminology for the entire Section. If the Working Group’s proposal is accepted following

review of the Preprint 2002 Proposals, the entire section will be revised to more

specifically refer to the terminology the Working Group chose for each occurrence of

these words.

CP 2336 (Page 203)

Subject: re Rule 235C2b (Clearances for Wires, Conductors, or Cables Carried on the

Same Supporting Structure – Vertical Clearance Between Line Conductors –

Sag-Related Clearances) and addition of a new method of calculating loading for

determining sag clearances

Proposal: This proposal includes significant changes in the method of determining the

maximum sag for installations where the voltage is more than 50 kV between

conductors. Under the proposed revision, the designer must consider both a line’s

upper and lower conductors’ summer and winter loading conditions and, from the

results, design for the greater vertical clearance determined for the structure. The

current Rule only involves determining the maximum final sag of the upper conductor
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with the maximum sag of the lower conductor under the same ambient conditions. The

current Rule could result in focusing on summer conditions when winter loading

conditions may be more severe.

Subcommittee Action: Subcommittee 4 accepted this proposal as submitted.

CP 2138 (Page 210)

Subject: Rule 235C2b(1)(a) (Clearances for Wires, Conductors, or Cables Carried on

the Same Supporting Structure – Vertical Clearance Between Line Conductors –

Sag-Related Clearances), this Rule’s Exception, and Footnote 1 of Table 238-1 and

bonding interval requirements

Proposal: This proposal recommends Including in the exception to Rule 2352b(1)(a)

and Footnote 1 of Table 238-1 wording indicating that the supply neutral or messenger

must be bonded to the communication messenger at the intervals specified in Rule 92C.

The current requirement makes it seem as though the reduced sag clearance allowed by

the exception would apply when the neutral/messenger bonding exists at one structure.

The proposed change makes certain that the bonding is performed at specific intervals

(four or eight times per mile depending on messenger conductivity) along a well-defined

area, not at just one or two structures.

Subcommittee Action: Subcommittee 4 accepted a modified version of the proposal.

The proposed wording of the exception provided was accepted as submitted.

Subcommittee 4 modified the proposed wording for the Footnote 1 slightly but satisfied

the intent of the CP.

CP 2167 (Page 212)

Subject: New Rules 235C4 (Clearances for Wires, Conductors, or Cables Carried on

the Same Supporting Structure) and 238E (Vertical Clearance Between Certain

Communications and Supply Facilities Located on the Same Structure), and worker

safety zones

Proposal: Create two new Rules 235C4 and 238E which advise of a worker safety zone

that cannot be violated with location of facilities or equipment.
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Subcommittee Action: Subcommittee 4 accepted this proposal by proposing to include

the following wording in new Rules 235C4 and 238E:

Communications Worker safety Zone

The clearance specifications of Rules 235C and 238 create a communication

worker safety zone between the facilities located in the supply space and

facilities located in the communication space, both at the structure and in the

span between structures. Except as allowed by Rules 238C and 238D and 239,

no supply or communication facility shall be located in the communication worker

safety zone.

CP 2151 (Page 236)

Subject: Rules 250 (General Loading Requirements and Maps) A1 (General) and

C (Extreme Wind Loading) and significant changes in loading requirements

Proposal: This proposal includes revising Rule 250A1 such that the two methods of

calculating wind loads contained in Rules 250B and 250C be used for calculations and

the result having greatest effect be used in line design. The changed proposed for Rule

250 C involves removing reference to support facilities exceeding 18 meters (60 feet)

above ground or water level. This change means that extreme loading has to be

calculated for all structures no matter what height above ground or water.

Subcommittee Action: Subcommittee 5 did not act on this proposal and instead

included it in the Preprint 2002 Proposals for public comment.

The current Rule requires both methods of calculation be used only if both Rules apply

to the design under consideration and the calculations are only necessary for structures

taller than 18 meters (60 feet). This proposed Rule will necessitate calculations for all

structures no matter what their height. This proposal does not provide any distinction

between Grade B and Grade C construction and, thus, introduces a significant change in

NESC policy as a result. If included in the final version of the 2002 NESC, these

changes could result in a distribution line being required to have the same strength as a

transmission line, if extreme winds control the design. In such circumstances, such a

change could also affect distribution line construction costs.

CP 2308 (Page 238)

Subject: Rule 250A3 (General Loading Requirements and Maps – General) and

addition of a statistical 50 Year return period

Proposal: This proposal includes addition of wording in Rule 250A3 that allows

designers to use statistical ice and wind data base information where available in lieu of

the requirements specified in Rule 250C. The information must cover a statistical

minimum 50-year return period.
14

Subcommittee Action: Subcommittee 5 accepted a modified version of the proposal

which will allow designers to use loading determined from available, analyzed, 50-year

weather data in lieu of the requirements specified in NESC Section 25.

CP 2394 (Page 239)

Subject: new Rule 250A4 (General Loading Requirements and Maps) and earthquake

ground motions

Proposal: This proposal includes revising Rule 250A by adding new Subparagraph 4:

4. The structural capacity provided by meeting the loading and strength

requirements of Sections 25 and 26 provides sufficient capability to resist

earthquake ground motions.

Subcommittee Action: Subcommittee 5 accepted the proposal as submitted.

CP 2306 (Page 241)

Subject: Rule 250C (General Loading Requirements and Maps) and extreme wind

loading for all material structure types

Proposal: This proposal includes language that would require all structure material

types (prestressed concrete, steel, etc.,) greater than 18 meters (60 feet) in height to be

designed to withstand, without conductors, the extreme wind load in Rule 250C in any

direction. The current code only requires this loading design for wood structures.

Subcommittee Action: Subcommittee 5 accepted the proposal in principal. The

subcommittee is proposing to require all structures in excess of 18 m (60 ft.,) no matter

what material type, to be designed to withstand the Rule 250C extreme wind load

(without conductors) in any direction by revising Rule 250C as follows:

B. Extreme Wind Loading

If no portion of a structure or its supported facilities exceeds 18 m (60 ft.)

above ground or water level, the provisions of this Rule are not required,

except as specified by the addition in Rule 261A1c or Rule 261A2f.

Subcommittee 5 also added a new Rule, Rule 261A2f which is to read exactly as

present Rule 261A1c.

CP 2307 (Page 242)

Subject: Rule 250C (General Loading Requirements and Maps) and extreme wind

loading for single pole structures

Proposal: This proposal includes wording to make Rule 250C applicable to only a single

pole structure by inserting "single pole" before the word "structure" in Rule 250C. The

reasoning provided focused on how the various methods of calculating wind loads on a
15

single structure (less than 18 m [60 ft.]) seldom result in loads being as critical as the

combined wind and ice loads design required by Rules 250B, 253, and 261.

Subcommittee Action: Subcommittee 5 accepted this proposal as submitted.

CPs 2309 (Page 250) and 2363 (Page244)

Subject: Rules 250B (Loadings for Grades B and C - General Loading Requirements

and Maps - Combined Ice and Wind Loading) and 250C (Loadings for Grades B and C -

General Loading Requirements and Maps – Extreme Wind Loading) and new equations

for extreme wind loading calculations and addition of a new map

Proposal: CP 2309 involves creating a new Rule 250D entitled, “Extreme Ice Plus Wind

Loading.” This new Rule would require calculation of vertical and horizontal wind and

tension loads utilizing a new 50-Year wind map. CP 2363 proposes significant change

and addition to Rule 250C which would incorporate new formulas for calculating wind

pressure and use of data from a 50-Year wind map based on a 3-second wind gust with

probability factoring included. New tables and charts are also included to assist in

making the calculations.

Subcommittee Action: Subcommittee 5 accepted modified versions of these proposals.

Instead of creating a new Rule 250D the Subcommittee proposed revision of Rule 250B

such that it now includes two alternative methods for determining loads for combined Ice

and wind loading. Either method may be used. Method 1 consists of current Rule 250B;

Method 2 includes the CP 2309 proposed method and use of the proposed 50-Year wind

map data. The Subcommittee modified the CP 2363 proposal but essentially Rule 250C

will involve use of a new equation and data from the also introduced 50-Year wind map.

Although the 50-Year wind map proposed provides a sound basis for selecting extreme

ice and wind loads, RUS voted against including the map in the NESC as a requirement

because the map is incomplete. RUS believes that the 50-Year map should be included

for information only in an NESC Appendix until the map is more complete. Concern was

expressed for these proposals on a number of other fronts. The proposals can

significantly reduce the required strength for Grade B wood structures in many parts of

the country. The new equation for calculating wind loads can become significantly

complicated. The alternative methods for determining loads for combined Ice and wind

loading can, under some scenarios, provide significantly different results and, thus, raise

questions about their equivalency.

CPs 2287 (Page 260), 2384 (Page 264), 2233 (Page 268), and 2230 (Page 268)

Subject: Table 253-1 (Overload Factors for Structures, Crossarms, Guys, Foundations,

and Anchors to Be Used with the Strength Factors of Table 261-1A) and a revision to

include other materials

Proposal: These four proposals include revision of Table 253-1. CPs 2287 and 2230

propose increasing the Grade C, Rule 250B Vertical Load, load factor requirement from

1.5 to 1.9. These two CPs also propose adding a new Footnote 6 (to the proposed

upgraded "1.9" load factor value) which advises the reader to use a value of 1.5 for
16

metal and prestressed concrete structures and crossarms, guys, foundations, and

anchors. CP 2219 proposes to amend Footnote 5 such that readers are advised to use

a value of 1.5 for fiber-reinforced composite structures and crossarms. CP 2384

provided considerable changes to Tables 253-1, 253-2, and 261-1A, all to obtain

equivalent and consistent levels of safety between wood and reinforced concrete and

between steel and prestressed concrete poles for both Grade B and Grade C

construction. CP 2233 proposes a change in Footnote 4 of Table 253-1 that removed

"wood and reinforced (not prestressed) concrete" from the footnote. Footnote 4

addresses a reduced strength requirement allowed at structures other than structures

installed at crossings.

Subcommittee Action: Subcommittee 5 accepted all of these proposals in principal and

proposed revision of the NESC that will result in a more uniformly applied requirements

for the various types of material structures as intended by the four CPs.

CP 2241 (Page 276)

Subject: Rule 261(Strength Requirements – Grade B and C Construction) and inclusion

of reference to new ANSI 05 Wood Product documents

Proposal: This proposal includes suggested changes of wording throughout Rule 261 to

include reference to expected revisions of ANSI 05.1, 05.2, and 05.3 specifications for

the design of wood pole, laminated wood and wood crossarms, respectively.

Subcommittee Action: Subcommittee 5 accepted the proposal in principal with full

acceptance contingent upon publication of the ANSI 05 documents and the public

comments received in response to the ANSI 05 documents' review.

CPs 2219 (Page 263), 2220 (Page 278), 2221 (Page 286) and 2222 (Page 296)

Subject: Rules 261A1 (Strength Requirements – Grade B and C Construction –

Supporting Structures), 261C1 (Strength Requirements – Grade B and C Construction –

Strength of Guys and Guy Insulators) and Table 261-1A (Strength Factors for

Structures, Crossarms, Guys, Foundations, and Anchors for Use with Overload factors

of Table 253-1) and addition of Fiber-reinforced composite structures

Proposal: These proposals include revising current Rules 261A1 and 261C1 and Table

261-1A to add Fiber-Reinforced Composite Structures to the requirements.

Subcommittee Action: Subcommittee 5 accepted the proposals in principal by creating

a new Rules 261A3 and 261C3 entitled, " Fiber-Reinforced Composite Structures."
17

CP 2365 (Page 282)

Subject: Rule 261A1e (Strength Requirements – Grades B and C Construction –

Supporting Structures – Metal, Prestressed-, and Reinforced-Concrete Structures) and

addition of spliced and reinforced structures

Proposal: This proposal includes adding a new Rule 261A1d which would allow

permanent splices or reinforcements of structures other than just wood poles as is now

allowed. The proposal also added wording to require splices/reinforcements of all

material types to obtain the required strength.

Subcommittee Action: Subcommittee 5 accepted a modified version of the proposal

that accomplished the proposer's intent.

CP 2154 (Page 288)

Subject: Rule 261H1 (Overhead Supply Conductors and Overhead Shield Conductors)

and Tables 261-3 (Conductor Sizes) and 261-4 (Communication Wire Sizes with

Respect to Loading District and Span Length) and inclusion of ACSR and Aluminum

conductor

Proposal: This proposal recommends that the Subcommittee either add values for

ACSR and all aluminum conductors in Tables 261-3 and -4 or delete the tables and

reference to Rules 261H and 261J. The CP suggested that the NESC should be

updated for these modern conductors.

Subcommittee Action: Subcommittee 5 accepted this proposal by deleting the two

tables and Rule 261H1 and by modifying Rule 261J, 261L2a, and 263E1a(2).

CP 2400 (Page 299)

Subject: Table 261-1A (Strength Factors for Structures, Crossarms, Guys, Foundations,

and Anchors for Use with Overload factors of Table 253-1) and inclusion of notes to

dispel confusion regarding the strength required "when installed" and "after degradation"

Proposal: This proposal includes significant editing of the existing notes for

Table 261-1A. The purpose of the proposed editing is to clear up confusion regarding

reference to the strength required "when installed" and "after degradation" provisions.

Subcommittee Action: Subcommittee 5 accepted a modified version of the proposal by

adding the following text to Table 261-1A:

(It is recognized that structures will experience some level of deterioration after

installation, depending upon materials, maintenance, and service conditions.

The table values specify strengths required at installation. Footnotes specify

deterioration allowed for wood and reinforced-concrete structures. Structures of

other materials shall be both installed and maintained to meet the table values.
18

When new or changed facilities add loads to existing structures (a) the strength

of the structure when new shall have been great enough to support the additional

loads and (b) the strength of the deteriorated structure shall exceed the strength

required at replacement. If either (a) or (b) cannot be met, the structure must be

replaced, augmented, or rehabilitated.)

CP 2156 (Page 317)

Subject: Rule 314B (General Requirements Applying to Underground Lines –

Grounding of Circuits and Equipment – Conductive Parts to Be Grounded) and

grounding riser guards exposed to contact with supply conductors

Proposal: This proposal includes adding to Rule 314B the wording "or are exposed to

contact with open supply conductors of greater than 300 V." The Rule would require

conductive-material ducts and riser guards that enclose electric supply lines or that are

exposed to contact with open supply conductors of greater than 300 V to be effectively

grounded. Communications risers do not have to be effectively grounded now.

Subcommittee Action: Subcommittee 7 accepted this proposal as presented.

CP 2104 (Page 332)

Subject: Rule 323E3 (Manholes, Handholes, and Vaults - Covers) and adding warning

signs in vaults and tunnels

Proposal: This proposal includes adding a recommendation to Rule 323E3 that advises

"when vaults and utility tunnels contain exposed live parts, a prominent Caution or other

appropriate warning sign should be posted where visible before entering the vault.

Subcommittee Action: Subcommittee 7 accepted this proposal by modifying

Rule 323E3 by adding the following sentence and Note:

When vaults and utility tunnels contain exposed live parts, a prominent safety

sign shall be posted where visible before entering the vault.

NOTE: ANSI Z535.1-1991, ANSI Z535.2-1991, ANSI Z535.3-1991,

ANSI Z535.4-1991, and ANSI Z535.5-1991 contain information regarding safety

signs.

CPs 2196 (Page 344) and 2200 (Page 351)

Subject: Rules 352 (Separations From Other Underground Structures) and

354 (Random Separation-Additional Requirements) and separation of cable and

underground structures

Proposal: These two proposals include revision of Rules 352 and 354 to remove

mention of horizontal and vertical and, instead, provide provisions for the radial

separation requirements of underground cable from other structures and cables. The
19

proposals also would change the Rule titles and the format of the NESC in this

underground topic. The proposed new titles are Rule 352, “Deliberate

Separations-Equal to or Greater than 300 mm (12 In.),” and Rule 354, “Random

Separation-Separation Less Than 300 mm (12 in.) From Underground Structures and

Other Cables.” The proposals also included gas lines as structures to recognize the

need for safety in installation.

Subcommittee Action: Subcommittee 7 accepted these proposals as presented.

CP 2201 (Page 352)

Subject: Rule 354D (Random Separation-Additional Requirements – Supply and

Communication Cables or Conductors) and a new exception for random burial of entirely

dielectric fiber-optic cables with supply cables

Proposal: This proposal adds an exception to Rule 354D to allow random separation of

supply cables or conductors and entirely dielectric fiber-optic communication cables with

no deliberate separation and no additional requirements, provided all parties are in

agreement.

Subcommittee Action: Subcommittee 7 accepted the proposal with modification. The

Subcommittee proposed changing the wording to require the installation to comply with

Rules 354D1a, b, and d. These Rules refer to grounded systems not operating in

excess of 22,000 V to ground, ungrounded system not being operated in excess of

5,300 V phase-to-phase, and ungrounded systems operating above 300 V between

conductors being equipped with a ground-fault indication system, respectively.

CP 2341 (Page 356)

Subject: Rule 380D (Safety Rules for Underground Lines – Equipment – General) and

padmounted equipment location re fire hydrants

Proposal: This proposal includes adding a new Rule 380D which states that

padmounted equipment, pedestals, and other above ground enclosures should be

located not less than 1.2 meters (4 feet) from fire hydrants. An exception was also

included that states where conditions do not permit a clearance of 1.2 meters (4 feet,) a

clearance of no closer than 0.9 meters (3 feet) is allowed.

Subcommittee Action: Subcommittee 7 accepted this proposal as submitted.

CP 2342 (Page 357)

Subject: Rule 381G (Safety Rules for Underground Lines – Equipment – Design –

Pad-Mounted Equipment) and locking of above ground enclosures

Proposal: This proposal includes adding to Rule 381G "other above ground" equipment

in addition to padmounted equipment shall have an enclosure that is either locked or

otherwise secured against unauthorized entry.
20

Subcommittee Action: Subcommittee 7 accepted this proposal by editing the proposed

text so the Rule refers to padmounted equipment enclosures and supply pedestals.

CP 2356 (Page 361)

Subject: Rule 410A2 (Safety Rules for Underground Lines – Supply and

Communications Systems – Rules for Employers - General) and establishment of

specific safety requirements

Proposal: This proposal includes a revision of Rule 410A2 to require employers to see

to it that work is performed in a safe manner, be in compliance with Section 42, and

have a mechanism for retraining of employees when necessary.

Subcommittee Action: Subcommittee 8 accepted this proposal in principal by providing

the following edited version of Rule 410A2 with the underlined portion being the new

requirements added by this proposal and Subcommittee action:

2. The employer shall provide training to all employees who work in the vicinity

of exposed energized facilities. The training shall include applicable work

rules required by this Part and other mandatory referenced standards or

rules. The employer will ensure that each employee has demonstrated

proficiency in required tasks. The employer shall provide retraining for any

employee who, as a result of routine observance of work practices, is not

following work rules.

CP 2349 (Page 373)

Subject: new Rule 423D5 (Underground Line Operating Procedures) and requiring

shoring of excavations

Proposal: This proposal includes creation of a new Rule 4235D which would require

shoring, sloping, or benching methods be used to protect employees when employees

are required to perform tasks in trenches or excavations in excess of 1.5 meters (5 feet)

in depth.

Subcommittee Action: Subcommittee 8 accepted this proposal in principal by providing

the following revised new Rule 423D5:

5. When a worker is required to perform tasks in trenches or excavations where

a cave-in hazard exists, or the trench or excavation is in excess of 1.5 m

(5 ft.) in depth, then shoring, sloping, or benching methods shall be used to

provide employee protection.
21

CP 2123 (Page 379)

Subject: Rule 441 (Additional Rules for Supply Employees – Energized Conductors or

Parts) and transient overvoltage studies for high voltage switching

Proposal: This proposal included adding a note to Table 441-1, “AC Live Work

Minimum Approach Distance” to advise that minimum approach distances for 3 phase

reclosing into trapped charges on 121 kV to 362 kV single break per pole switching

devices have to be determined by transient overvoltage studies.

Subcommittee Action: Subcommittee 8 accepted this proposal in principal and rather

than include a Rule in a Table revised Rule 441A3b to read as follows:

4. Transient Overvoltages Above 72.5 kV

a. For 121 kV to 362 kV single break per pole switching devices with

3 phase reclosing into trapped charges the maximum per-unit values

given in the table (3 per unit for 121 to 362 kV) may increase

significantly. Minimum approach distances for these devices shall be

determined by a transient overvoltage study.

Note: These overvoltages will not exceed the values of Table 441-1 if

reclosing is blocked.

CP 2385 (Page 386)

Subject: Rule 441A3b (Additional Rules for Supply Employees – Energized Conductors

or Parts – Approach Distance to Live Parts) and adding a "Maximum Use Voltage"

requirement for rubber gloves

Proposal: This proposal would revise Rule 441A3b such that rubber gloves and sleeves

must be insulated for the "Maximum Use Voltage" which is specified in a new

Table 441-6 which was also Included with the proposal.

Subcommittee Action: Subcommittee 8 accepted this proposal as submitted.

CP 2355 (Page 387)

Subject: Rule 441A3b (Additional Rules for Supply Employees – Energized Conductors

or Parts – Approach Distance to Live Parts) and addition of a requirement for

supplemental insulation when working at voltages above 15 kV

Proposal: This proposal included adding a new paragraph to Rule 441A3 which would

require use of supplementary insulation, tested for the maximum working voltage at the

work site, to be used to support the worker.

Subcommittee Action: Subcommittee 8 accepted the proposal in principal by providing

the following new Rule 441A3C to read as follows:
22

c. When the rubber glove work method is employed at voltages above 15 kV

phase to phase, supplementary insulation, (e.g., insulated aerial device or

structure-mounted insulating work platform), tested for the voltage involved,

shall be used to support the worker.

CP 2372 (Page 411)

Subject: reorganization of Sections 25, 26, and 27 on Loading and Strength

Proposal: NESC Subcommittee 5 Working Group 5.2 submitted expansive full text

revisions of Sections 25, 26, and 27. The proposal eliminates use of the “Light,”

“Medium,” and “Heavy” loading districts concept and introduces in their place a

“Construction,” Extreme Wind,” and “Extreme Wind and Ice” concept. The proposal also

includes introduction of an alternative method of determining strength factors and new

wind maps and tables to be used for calculating structure loading requirements. Unlike

all other proposals in the Preprint 2002 Proposals publication, CP 2372 includes

no "Supporting Comment" from the submitter to justify the need or purpose for

the changes proposed.

Subcommittee Action: Subcommittee 5 accepted this proposal as modified at an April,

1999, Subcommittee 5 meeting. A review of the explanations for some subcommittee

members' votes is interesting. One Subcommittee 5 member voted in favor of this

proposal to allow it to obtain public review and comment. Several Subcommittee 5

members voted against this proposal because they felt that it was incomplete, as written.

These negative voting members also claimed that the proposal contains material and

requirements that are going to introduce confusion to readers because, among other

reasons, the alternative calculation method will produce results that differ from the

method already included in the NESC. Concern was also expressed for the added

weather maps not being complete for certain portions of the U.S.

Because this proposal includes potentially significant changes which may have

significant impact on the design and cost of electric utility plant, RUS recommends that

borrowers read this CP and submit their comments by May 1, 2000.
BIOGRAPHICAL SKETCH

GEORGE J. BAGNALL

George Bagnall was appointed Director of the Electric Staff Division (ESD) in May of

1994.

In this capacity, George is responsible for development of RUS standards, specifications,

and technical guidance documents for electric distribution and transmission systems.

George also assists in the development of RUS policies and procedures relating to

engineering planning, design, and construction of electric distribution and transmission

systems.

Prior to this appointment, George spent:

• 8 years as Chief of the Engineering Standards Branch, and (concurrently)

Chairman of Technical Standards Committee ”A” in the RUS

Telecommunications Program;

• 4 years as Distribution and Transmission Engineering Branch Chief in the

former Western Area Electric; and

• 17 years in ESD (with a 2 year break in the US Army) ending as Chief of

ESD’s Engineering Services Branch.

Mr. Bagnall is:

• A Senior Member of the Institute of Electrical and Electronics Engineers;

• A member of NACE the Corrosion Society, and

Represents RUS on the National Electrical Safety Code.
COMMENT on

PROPOSAL FOR REVISION of

2002 Edition,

NATIONAL ELECTRICAL SAFETY CODE

(A separate form must be used for each Comment)

CHANGE PROPOSAL No. RULE

COMMENT:

SUBMITTER:

Name Date

Company

Address

City/State/Zip

Organization Represented (if any)

Mail to: Secretary, NESC Committee, IEEE Standards Department,

445 Hoes Lane, P.O. Box 1331, Piscataway, NJ 08855-1331

Fax: 732-562-1571

This form may be duplicated. A diskette containing the comment text in any

electronic form should be submitted, in addition to the hard copy.
	




	






	

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