1、National Electrical Safety CodeC2-20123 Park Avenue, New York, NY 10016-5997, USAAccreditedStandardsCommitteeC2-2012National Electrical Safety CodeSecretariatInstitute of Electrical and Electronics Engineers, Inc.Approved 14 April 2011Institute of Electrical and Electronics Engineers, Inc.Approved 3
2、 June 2011American National Standards Institute2012 EditionAbstract: This Code covers basic provisions for safeguarding of persons from hazards arising from theinstallation, operation, or maintenance of (1) conductors and equipment in electric supply stations, and(2) overhead and underground electri
3、c supply and communication lines. It also includes work rules for theconstruction, maintenance, and operation of electric supply and communication lines and equipment. TheCode is applicable to the systems and equipment operated by utilities, or similar systems and equipment, ofan industrial establis
4、hment or complex under the control of qualified persons. This Code consists of theintroduction, definitions, grounding rules, list of referenced and bibliographic documents, and Parts 1, 2, 3,and 4 of the 2012 Edition of the National Electrical Safety Code.Keywords: communications industry safety; c
5、onstruction of communication lines; construction of electricsupply lines; electrical safety; electric supply stations; electric utility stations; high-voltage safety; operation ofcommunications systems; operation of electric supply systems; power station equipment; power stationsafety; public utilit
6、y safety; safety work rules; underground communication line safety; underground electricline safety1 August 2011 STDPT97085The Institute of Electrical and Electronics Engineers, Inc.3 Park Avenue, New York, NY 10016-5997, USACopyright 2011 by the Institute of Electrical and Electronics Engineers, In
7、c.All rights reserved. Published 2011Printed in the United States of AmericaNational Electrical Safety Code and NESC are registered trademarks and service marks in the U.S. Patent Part 2 was a 7th edition;Part 3 was a revision of the 6th edition; Part 2, Section 29, did not cover the same subject ma
8、tter as the 5thedition; and Part 3 was withdrawn in 1970. In the 1987 Edition, revisions were made in all parts, andrevisions to all parts have been made in subsequent editions. It is therefore recommended that reference tothe NESC be made solely by the year of the published volume and desired part
9、number. Separate copies ofthe individual parts are not available.Work on the NESC started in 1913 at the National Bureau of Standards (NBS), resulting in the publicationof NBS Circular 49. The last complete edition of the Code (the 5th edition, NBS Handbook H30) was issuedin 1948, although separate
10、portions had been available at various times starting in 1938. Part 2Definitionsand the Grounding Rules, 6th edition, were issued as NBS Handbook H81, ANSI C2.2-1960, in November1961, but work on other parts was not actively in process again until 1970.In 1970 the C2 Committee decided to delete the
11、Rules for the Installation and Maintenance of ElectricUtilization Equipment (Part 3 of the 5th edition), now largely covered by the National Electrical Code(NEC) (NFPA 70, 2011 Edition), and the Rules for Radio Installation (Part 5 of the 5th edition) fromfuture editions.qThe Discussion of the NESC,
12、 issued as NBS Handbook H4 (1928 Edition) for the 4thedition of the NESC and as NBS Handbook H39 for Part 2 of the Grounding Rules of the 5th edition, wasnot published for the 6th edition.The 1981 Edition included major changes in Parts 1, 2, and 3, minor changes in Part 4, and the incorporationof t
13、he rules common to all parts into Section 1. The 1984 Edition was revised to update all references and tolist those references in a new Section 3. Converted metric values, for information only, were added. Gender-related terminology was deleted. Section 1Introduction, Section 2Definitions, Section 3
14、References,and Section 9Grounding Methods, were made applicable to each of the Parts 1, 2, 3, and 4.The 1987 Edition was revised extensively. Definitions were changed or added. Requirements affectinggrounding methods, electric supply stations, overhead line clearances and loading, underground lines,
15、 andwork rules were revised.The 1990 Edition included several major changes. General rules were revised. A significant change to themethod for specifying overhead line clearances was made and the rationale added as Appendix A.Requirements for clearances of overhead lines from grain bins and an alter
16、nate method for determining thestrength requirements for wood structures was added. Rules covering grounding methods, electric supplystations, underground lines, and work rules were changed.In the 1993 Edition, changes were made in the rules applicable to emergency and temporary installations. InSec
17、tion 9 and Parts 1, 2, and 3, rules were extended or clarified to include HVDC systems. The requirementsfor random separation of direct-buried supply and communications systems were modified for consistencyand clarity, as was the rule in Part 4 on tagging electric supply circuits.In the 1997 Edition
18、, the most notable general change that took place is that numerical values in the metric(SI) system are shown in the preferred position, with customary inch-foot-pound values (inside parentheses)qInformation on references can be found in Section 3.This foreword is not a part of Accredited Standards
19、Committee C2-2012, National Electrical Safety Code.iv Copyright 2011 IEEE. All rights reserved.following. A bibliography, Appendix B, which consists of a list of resources identified in notes orrecommendations, was added. Changes were made to rules affecting grounding, electric supply stations, ando
20、verhead lines, particularly with regard to clearance rules applicable to emergency and temporaryinstallations. Strength requirements contained in Sections 24, 25, and 26 were revised completely.Underground line requirements for random separation for underground lines of direct-buried cables weremodi
21、fied. The requirement for cable identification marking by means of sequentially placed logos wasintroduced. Work rules added a requirement that warning signs and tags comply with applicable ANSIstandards, tagging requirements were clarified with regard to SCADA, and extensive requirements for fallpr
22、otection were added.In the 2002 Edition, several changes were made that affected all or several parts of the Code. Particularly,this edition clarifies interfaces between the NEC and NESC with regard to Code jurisdiction in the area ofstreet lights and area lights. Also included is clarification for
23、situations between utility workers and theirauthorized contractors and installations on industrial complexes.The major revisions for the 2007 Edition included grounding, moving sag calculations to Section 23,moving guy and span wires insulator rules to Section 21, phasing out of the alternate method
24、 for load factorsand strength factors, flammable materials transported, phase-to-phase cover-up, and minimum approachdistance tables.In the 2012 Edition, major changes include an updated scope, application, and definitions; greatly simplifiedminimum approach tables and voltage exposure for arc flash
25、; the addition of K factor for wire attention; andadded clarification of the ungrounded portions of guys and swimming pools.The Scope, Application, and Definition rules were extensively revised in 2012 to better reflect the historicalapplication of the NESCin large measure to clarify the relative ap
26、plicability of the NESC versus the NEC.The changes in language in Rules 010Purpose and 011Scope are not changes in either scope orpurpose; they are clear statements of the almost 100-year application of the requirements of the NESC to thespecified circumstances. Additional rules were changed for cla
27、rity or to support changes made in othersections of the Code.In Rule 091, revisions were made to clarify where rules require conductors or equipment to be effectivelygrounded, meeting the requirements of Section 9, plus the definition of effectively grounded must be met.In Rule 094B7, the length and
28、 thickness requirements for using a directly embedded metal pole as anacceptable grounding electrode were deleted. Text was added to specify the distance required for asupplemental ground electrode to be installed with an embedded metal pole. Also, the Exception within theRule added the words “or ty
29、pe metal” that recognize other length, configuration, and material may beallowed if supported by a qualified engineering study. In Rule 099B, the grounding electrode conductor for grounding communication apparatus was changed froman AWG No. 14 to AWG No. 6. The revisions in Part 1 consisted of impro
30、ving Rule 110A2 to reduce clearance to live parts for animpenetrable fence and simplifying the Table 111-1 list of illumination levels for generating stations andsubstations.Additional revisions were also made as follows: Updating the standard revision dates that contain information regarding safety
31、 signs. Storing material, equipment, and vehicles in supply stations. Outdoor lighting at unattended stations (not required).Copyright 2011 IEEE. All rights reserved. v Noting that permanently installed fire-extinguishing equipment is not a requirement. Use of “taut-string distance” measurements for
32、 vertical clearances to energized part.Rule 214A5 was revised; multiple change proposals attempted to add consistency to the application of theterms grounded and effectively grounded. Subcommittee 4 retained both terms and retained the requirementthat guys be effectively grounded. Subcommittee 4 als
33、o revised Rules 215B1 and 215B2, applied a revisionto the application of guy insulators, and clarified the voltage between line conductors.A footnote to Table 251-1 was inserted to clarify the application of the K factor for wire tensions when amessenger supports multiple conductors using spaces. It
34、 states that when each conductor is separatelyloaded with ice and wind as described in Rule 251A3b, the K factor should be applied to all cables. Rule 261H1 addresses tensions of overhead supply conductors and shield wires. One change proposal addedtension limits when Rule 250C and Rule 250D loads a
35、pply. Similar to what already existed for splices anddeadend fittings, conductors and shield wires will now be limited to 80% of the rated breaking strengthwhen those extreme load conditions are applied along with a load factor of 1.0. Another change in the samerule modified the application of the s
36、econdary conductor tension limits from 16 C (60 F) to the applicabletemperature listed in Table 250-1 for Rule 250B district loads. Reducing the temperatures at which tensionlimits are applied is in line with recommendations from conductor manufacturers and will reduce the risk ofconductor damage du
37、e to aeolian vibration.Rule 313 was reworded to include the recording and correction of conditions, not just defects, that affectcompliance with the Code. In Rule 314B, the voltage level for grounding riser guards and ducts was deleted.Rule 320B5 now requires not less than 300 mm (12 in) separation
38、from gas and other lines that transportflammable materials. New Rule 323E5 requires clearances based on Rule 110A2 for aboveground vaultswith ventilation opening not protected with baffles or louvers. Figure 323-1 and Figure 323-2 were revisedto comply with the latest figures in ASTM C857. The title
39、 for Section 35 was revised to include cable in ductnot part of a conduit system. Recommendations concerning color coding for direct-buried cables and ductnot part of a conduit system were added to Rules 350F and 350G. Installation rules for cable in duct wereincluded in Rule 352. An Exception was a
40、dded to Rule 354A2 to allow less than 300 mm (12 in) separationbetween supply conductors operating at not more than 300 V between conductors and gas and other linesthat transport flammable materials where supplemental mechanical protection is provided. New Rule 355contains rules for duct not part of
41、 a conduit system. Rule 384 was rewritten to require bonding betweenaboveground metallic communication and supply enclosures only.Two significant changes were made to the work rules in Part 4, specifically in the Rule 441 minimumapproach distanced tables, and also in Rule 410A3 on arc flash exposure
42、. Revisions to IEEE Std 516-2009(NESCs source for calculated minimum approach distances) required changes to be made to the minimumapproach distances in Part 4. Prior NESC editions included several tables containing minimum approachdistances based on voltage levels and overvoltage levels. In the 201
43、2 Edition, the minimum approach tableshave been greatly simplified (accurate to the current IEEE 516 calculations) providing distances at theaccepted historic maximum overvoltage levels. An engineering study of circuit overvoltage will have to becompleted to use a reduced minimum approach distance.R
44、ule 410A3 was revised to recognize exposures at less than 1000 V. Significant testing was conducted bytwo separate major utilities and a research institute, providing the opportunity to establish appropriateincident energy levels for many common industry applications. The result of the review of the
45、 testingsupported the development of new Table 410-1 that establishes arc energy thresholds for differentequipment/exposures at voltage levels below 1000 V.Table A-1 of Appendix A was revised only in the manner of presentation by the Overhead ClearancesSubcommittee. However, the extreme wind calcula
46、tions of Appendix C were revised by the OverheadStrengths and Loadings Subcommittee to reflect changes in Rule 250C.vi Copyright 2011 IEEE. All rights reserved.Substantive changes in the 2012 Edition are identified by a bar in the left-hand margin. In several cases,rules have been relocated without
47、substantive changes in the wording. In these cases, only the rule numbershave been indicated as having been changed.The Institute of Electrical and Electronics Engineers, Inc., was designated as the administrative secretariatfor C2 in January 1973, assuming the functions formerly performed by the NB
48、S. Comments should be sentto the Secretary, National Electrical Safety Code Committee, through the following Contact Form:SecretaryNational Electrical Safety Code CommitteeInstitute of Electrical and Electronics Engineers, Inc.http:/standards.ieee.org/contact/form.htmlA representative Committee on I
49、nterpretations has been established to prepare replies to requests forinterpretation of the rules contained in the Code. Requests for interpretation should state the rule in question,as well as the conditions under which it is being applied. Interpretations are intended to clarify the intent ofspecific rules and are not intended to supply consulting information on the application of the Code. Requestsfor interpretation should be submitted using the NESC Interpretation Request Form on the NESC homepage: http:/standards.ieee.org/about/nesc/interps.html.If the requ
