Call for Comment

Call for Comment on Specific NESC Change Proposals

2-1-2020 some text of interest is highlighted / more coming

The publication of the 2022 NESC Preprint is an important opportunity for all stakeholders to provide comment on the Change Proposals (CPs) received and initial recommendations made by the NESC Subcommittees. As such, the broadest possible input is solicited and all interested and affected parties are encouraged to provide comment. For over 30 CPs, NESC Subcommittees have specifically requested public comment from affected interests.

Sections 1, 2, and 3

CP5049

Rule 010 C CP5049 seeks to clarify purpose (Rule 010) of the NESC with regard to abnormal events (e.g., weather). Public comments for this change proposal are encouraged.

CP5542,

Rule 017 A CP5542 recommends that customary units (inch-foot) units be placed in the primary position in NESC text, and that metric (SI) units be placed in the secondary position, in parentheses. The CP further recommends that separate customary and metric unit tables and figures be created, and that the metric tables and figures be placed in an annex or appendix. NESC Subcommittee 1 recommends the use of normative annexes for the next edition so that if separated, the metric tables will continue to be recognized as part of the Code. Public comments for this change proposal are encouraged.

CP5424,

Definition: joint use NESC Subcommittee 1 is requesting public comments on CP5424 for a definition of joint use, as the action taken by NESC Subcommittee 1 differs from the action taken by NESC Subcommittee 4.

CP5104,

Appendix B NESC Subcommittee 1 is seeking comments on CP5104. NESC Subcommittee 1 has no majority position, pending outcome of public comments on other change proposals addressing the k-factor. See also CP5570 and CP5571.

Section 9, Grounding Methods

CP5287, Rule 094 B2 NESC Subcommittee 2 recognizes the action taken on CP5287 represents a substantial change with regard to requirements for driven rods. NESC Subcommittee 2 seeks public comments especially in the form of analysis and consequences associated with this proposed rule change.

Part 1: Electric Supply Stations

CP 5006, Rules 140–146 NESC Subcommittee 3 seeks public comment on CP5006, a comprehensive revision of Section 14, Storage Batteries, to recognize new battery technologies, applications, and their hazards.

CP 5452, Rule 190 NESC Subcommittee 3 seeks public comment on CP5452, which proposes to replace the existing Section 19 with a new section covering new and emerging electric generation station technologies. The proposal’s initial focus is on photovoltaic (PV) generating stations.

Part 2: Installation and Maintenance of Overhead Electric Supply and Communication Lines

CP5096, Rule 215 C2, C3

NESC Subcommittee 4 is seeking public comment on CP5096. NESC Subcommittee 4 voted to reject this CP but the vote outcome was not a strong majority.

The proposal is to require line designers to consider a wide variety of field situations created by a broken or slake anchor guy wire. A majority of the subcommittee members felt the proposed rule could not be practically applied and would result in confusion for many designers. The CP as written is ineffective for the industry to universally apply and poorly understood on joint-use pole applications as seen in the 2012 Edition of the NESC. Effectively grounding and bonding the communication messenger to initiate the supply system protective devices is a better solution for safety. Communication work rules require a communication worker to test for voltage prior to performing work that mitigates the safety concern around “voltage transfer.” NESC Subcommittee 4 encourages individuals to consider the negative vote comments and offer public comments.

CP5332, Rule 233 C2, C3, C3c

See action taken on CP5196. This CP and CP5196 address identified issues within the Code but take differing approaches. The intent is to clarify the approach to increasing the clearance between conductors supported on different structures and where the voltage between the conductors exceeds 22 kV. NESC Subcommittee 4 is requesting specific comments on these two proposals during the public comment period.

CP5334, Rule 233 Table 233-1

See action taken on CP5196. This CP and CP5196 address identified issues within the Code but take differing approaches. The intent is to clarify the approach to increasing the clearance between conductors supported on different structures and where the voltage between the conductors exceeds 22 kV. NESC Subcommittee 4 is requesting specific comments on these two proposals during the public comment period.

CP5335, Rule 233 Table 233-2, Footnotes 1, 2

See action taken on CP5332. This CP and CP5332 address identified issues within the Code but take differing approaches. The intent is to clarify the approach to increasing the clearance between conductors supported on different structures and where the voltage between the conductors exceeds 22 kV. NESC Subcommittee 4 is requesting specific comments on these two proposals during the public comment period.

CP5337, Rule 233 Table 233-3

See action taken on CP5332. This CP and CP5332 address identified issues within the Code but take differing approaches. The intent is to clarify the approach to increasing the clearance between conductors supported on different structures and where the voltage between the conductors exceeds 22 kV. NESC Subcommittee 4 is requesting specific comments on these two proposals during the public comment period.

CP5591, Rule 234 Table 234-1

NESC Subcommittee 4 believes CP5591 presents a positive approach to considering conductor wind displacement for clearances to buildings, but that it is not fully developed regarding supporting structures. NESC Subcommittee 4 is seeking public comment on the general approach this CP is proposing.

CP5592, Rule 234 Table 234-2 NESC Subcommittee 4 feels CP5592 presents a positive approach to considering conductor wind displacement for clearances to buildings, but that it is not fully developed regarding supporting structures. NESC Subcommittee 4 is seeking public comment on the general approach this CP is proposing.

CP5595, Rule 224

A NESC Interpretation Request (IR) 575, Rule 224A and Rule 238D for the 2012 Edition was considered by the Interpretations Subcommittee but consensus could not be reached. NESC Subcommittee 4 formed a Task Force to prepare a report for inclusion in the Preprint for public comment. See CP5595, CP5603, and CP5604 for proposed changes to Rule 224A and Rule 235A2 as recommended by NESC Task Force 4.5.

CP5603, Rule 224 A

NESC Interpretation Request (IR) 575, Rule 224A and Rule 238D for the 2012 Edition was considered by the Interpretations Subcommittee but consensus could not be reached. NESC Subcommittee 4 formed a Task Force to prepare a report for inclusion in the Preprint for public comment. See CP5595, CP5603, and CP5604 for proposed changes to Rule 224A and Rule 235A2 as recommended by NESC Task Force 4.5.

CP5604, Rule 235 A2

NESC Interpretation Request (IR) 575, Rule 224A and Rule 238D for the 2012 Edition was considered by the Interpretations Subcommittee but consensus could not be reached. NESC Subcommittee 4 formed a Task Force to prepare a report for inclusion in the Preprint for public comment. See CP5595, CP5603, and CP5604 for proposed changes to Rule 224A and Rule 235A2 as recommended by NESC Task Force 4.5.

CP5027, Rule 238

NESC Subcommittee 4 is seeking public comment on the proposed changes. The intent of the subcommittee is to consolidate the antenna rules into a single location to clarify the required antenna rules and to treat antennas as equipment consistently throughout the Code.

CP5152, Rule 235 Table 235-6, row 2 The intent of this CP was to simplify the clearance rules for guys and guy anchors. NESC Subcommittee 4 believes that the modified CP is a first good step but specifically seeks comments on the proposed guy clearances.

CP5570, Rule 230 B4 (Subcommittee 4)

CP5571, Rule 251 B3 (Subcommittee 5) A Joint Subcommittee 4/5 WG was tasked with developing change proposals relative to the k-factor (additive constant) for several rules in Part 2. Public comment is invited for these CPs. Additionally, several other CPs were submitted relative to this topic: see CPs 5440, 5441, 5442, 5443, 5444, 5445, 5446, and 5447. The subcommittees are seeking the opinion of the professional electrical utility community as related to the following: — Does the k-factor require revision? — The impact of the CPs if implemented. — Data that would support your opinion. — Alternatives that could be considered by the Joint Subcommittee. — Do any of the related CPs noted above address the issue more effectively? See also CP5104.

CP5517, Rule 250 C

CP5589, Rule 250 C

CP5590, Rule 253

CP5267, Rule 253 NESC Subcommittee 5, through extensive discussion as to how to update Rule 250C, developed two approaches. Both CPs eliminate the Importance Factor (I = 1.0) from the equations. The Importance Factor is now included in the wind speed maps. The subcommittee is seeking to adopt a wind map philosophy that is consistent with Industry Standard ASCE 7-16 and Manual of Practice ASCE 74-19, and addresses the change in these documents for extreme wind maps and their implementation for the safety to utility workers and the public. The wind map currently used for Rule 250C in the NESC 2017 edition is a non-uniform hazard wind map combining wind hazards of 50-year MRI for continental winds, and approximately 90-year MRI for hurricane winds along the east and southeastern states.

CP5517 adopts the 100-year Mean Recurrence Interval (MRI) 3 s gust wind speed map of ASCE 7-16 (Appendix CC, Serviceability Considerations). This map would be applicable to both Grade B and Grade C, with Load Factors (LF) from Table 253-1 without Note 7. In general, the 100-year MRI map is not significantly different from the current map with some localized exceptions. Note that Table 253-1 contains a 0.87 load factor that is applied to the Rule 250C wind load for Grade C structures that effectively make the resultant comparable to a 50-year MRI wind. A load factor of 1.0 is applied for Grade B. Copyrighted and Authorized by IEEE. Restrictions Apply.

CP 5589 addresses the application of wind maps per the grade of construction, as follows: NESC Subcommittee 5 seeks the opinion of the professional utility engineering community as to the best approach between CPs 5517and 5590 and CPs 5589 and 5267.

CP5426, Rule 250 D NESC Subcommittee 5 would like feedback from those reviewing the proposed 2022 CPs as to any concerns with adopting the latest version of the 100-year Mean Recurrence Interval (MRI) Uniform Ice Thickness Map with 3 s gust speeds to be found in Manual of Practice ASCE 74-19.

CP5453, Rule 250 C

CP5454, Rule 250 D

CP5466, Rule 250 C

CP5467, Rule 250 D The listed CPs would, in effect, reduce or eliminate exemptions from the additional load cases listed on Rules 250C and 250D for structures supporting lines not exceeding 60 ft above local grade or water level. As shown in various load cases, structures supporting relatively small conductors are governed by Rule 250B. The Rule 250B loading district and applied grade of construction will determine which conductor sizes would be governed by Rule 250B loads versus Rules 250C and 250D load cases. As shown in the Preprint, SC5 modified both CPs 5453 and 5454 in such a fashion as to effectively avoid change to the current approaches to the structures supporting lines that do not exceed 60 ft above grade or water level.

NESC Subcommittee 5 would like feedback from the professional electrical utility community as related to the following:

— Do the original CPs have merit (prior to modification)?

— Would selective exemptions be appropriate? For example: Lines exceeding 22 kV to ground that cross rural/agricultural areas could be constructed to Grade C.

NESC Subcommittee 5 would like feedback from the professional electrical utility community on the concept of requiring all structures, regardless of height, to be subject to Rule 250C and Rule 250D load cases in addition to load cases of Rule 250B. — The impact of the CPs requiring all structures to be subject to Rules 250C and 250D load cases if implemented. — Data that would support this opinion. — Alternatives that could be considered by the Joint Subcommittee.

— Do any of the related CPs noted above address the issue more effectively? In particular, are CP5353 and CP5354 (discussed following) the most appropriate options?

— Should we simply leave the rules alone? Grade of construction ASCE 7-16 Mean Recurrence Interval (MRI) [3 s gust wind speed map recorded at 33 ft (10 m) above ground] B 100 year MRI in mph (m/s) with a LF = 1.0 C 50 year MRI in mph (m/s) with a LF = 1.0 Copyrighted and Authorized by IEEE. Restrictions Apply.

CP5467, Rule 250 D Based on discussion within NESC Subcommittee 5, there was concern as to the validity of applying exposure category B and the concept being more design-based in nature. Utilities would be unable to utilize exposure category B considering exposure categories may change over time. Moreover, industry experience has shown the effects of secondary damage to be largely responsible for failures on shorter structures during extreme wind or combined ice and wind events. Therefore the proposed change is not perceived to improve safety. The proposed change would present inconsistencies with the current gust response factors in the Code.

CP5465, Rule 250 A3 CP5471, Rule 250 Table 250-2 NESC Subcommittee 5 would like feedback from those reviewing the proposed 2022 CPs as to the value of including conditions for the use of ASCE 74-10 Exposure Category B for lines and structures that do not exceed 60 ft.

Part 3: Underground Lines

CP5411, Rule 315 A4 NESC Subcommittee 7 notes that the referenced standards, IEEE Std 487-2007, IEEE Standard for the Electrical Protection of Communications Facilities Serving Electric Supply Locations—General Considerations, and IEEE Std 1590-2003, IEEE Recommended Practice for the Electrical Protection of Communication Facilities Serving Electric Supply Locations Using Optical Fiber Systems, have been revised since 2007 and 2003. The most recent version of IEEE Std 487 is IEEE Std 487-2015 and the most recent version of IEEE Std 1590 is IEEE Std 1590-2009. NESC Subcommittee 7 seeks comments regarding whether it is appropriate to update the Note associated with this rule to identify the most current version of these IEEE standards.

CP5520, Rule 380 E This CP has the potential to require utilities to maintain different types of transformers with different insulating liquid types. Additionally, Rule 152A is in regard to substations generally under the control of a single entity and differs from the conditions associated with pad-mounted equipment near buildings. NESC Subcommittee 7 is also concerned that use of the term “minimized” is vague as part of a “shall” rule.

Part 4: Work Rules

CP5528, Rule 441 A3f Covering neutrals is required in Rule 441A3a; additional information is needed about covering conductive objects. NESC Subcommittee 8 will work with the submitter to respond to NESC Subcommittee 8’s questions in the public comment period, and also seeks additional public comment.

CP5600, Table 410-4 NESC Subcommittee 8 and Working Group 8.16 request public comment on CP5600 regarding a proposed new Table 410-4 that addresses live-front transformers, live-front terminations, and horizontally racked circuit breakers, based on recent new arc flash testing. NOTE: All submitted CPs are included in the Preprint. A number of proposals were withdrawn by the submitters during the NESC Subcommittee meetings that took place to review proposals. These withdrawn CPs are no longer open for comment, since there was no action taken by the cognizant subcommittee. They are included in the Preprint Proposals for the 2022 Edition of the NESC is a matter of historical record.