HomeMy WebLinkAboutGuide In Using The NESC 1984GUIDE IN USING THE NESC
F. A. Denbrock, P.E.
T. W. Williams, P.E.
Gilbert/Commonwealth
Jackson, Michigan 49201
Presented at the
Tennessee Valley Authority
1984 National Electrical Safety Code
Review/Seminar
Knoxville, Tennessee - July 14, 1984
NG@
ORIGIN AND HISTORY
ORIGIN AND HISTORY
HISTORICAL DEVELOPMENT
In 1913, Congress authorized the Bureau of Standards to study the hazards of electrical
practice. These studies resulted in the drafting of rules that became the National Electrical
Safety Code.
The plan followed was outlined in an announcement made at the Chicago Convention of the
National Electric Light Association in 1913. The rules in force in various European coun-
tries were studied and the books of rules in use by operating companies in this country were
collected and examined. A study of the technical papers and reports of committees of engi-
neering societies added substantially to the available material. A large number of formal and
informal conferences were held by the Bureau with representatives of state commissions,
engineers of operating utilities and manufacturers, and with interested associations.
The first rules were published in 1914 as Circular No. 49 of the Bureau of Standards. This
circular was entitled “Safety Rules to be Observed in the Operation and Maintenance of
Electrical Equipment and Lines.” The first paragraph of the introduction reads:
“The study of life and property hazards incident to the generation, distribution and use of
electrical energy includes the consideration of construction methods on the one hand and
of operating methods on the other. Improvements in construction and isolation of danger-
ous parts must be largely depended on for the protection of the uninstructed public, while
the safeguarding of operation and maintenance must remain the principal factor in the
safety of electrical workmen for whom isolation is necessarily less complete. To a lesser
extent the security of the public also must depend on the protective operating methods
employed and on the care of the electrical workers.”
The first paragraph of the scope of the rules reads:
“The following safety rules apply to the operation of, and work on or about, power and
signal lines, the electrical equipment of central stations, substations, private plants, electrical
tests, and tunnel, and subway or similar underground work.”
The Bureau of Standards continued its work and in 1915 issued Circular No. 54 entitled,
“Proposed National Electrical Safety Code.” It was labeled a preliminary edition submitted
for discussion and criticism. It contained Part 1, ‘“‘Rules for the Installation and Main-
tenance of Electric Supply Stations and Equipment”; Part 2, “‘Rules for the Installation and
Maintenance of Electric Supply and Signal Lines”; Part 3, “‘Rules for the Installation and
Maintenance of Electrical Utilization Equipment.’ Appendix A covered grounding methods
for stations, lines and utilization equipment.
A second edition of Circular No. 49 was published in May of 1915.
The second edition of Circular No. 54 was issued in November 1916 for examination, trial
and constructive criticism. This was a greatly expanded edition and included Parts 1, 2, 3
and 4, as well as a discussion of each part.
In 1918, NBS Circular No. 72, “Scope and Application of the National Electrical Safety
Code,” was issued.
1920-1930: An Active Period
The third edition of the NESC, dated October 31, 1920, was issued in 1921 as NBS Hand-
book No. 3. Handbook No. 4 with the same date was entitled ‘Discussion of the National
Electrical Safety Code.”
The fourth edition of the NESC, dated December 31, 1926, was published in 1927, still as
NBS Handbook No. 3. This revision of the code was carried out under the rules of pro-
cedure of the American Engineering Standards Committee and the revised code was
approved as an American Standard. Part 5, Rules for Radio Installations, was included in
that edition. The discussion of the fourth edition, still called NBS Handbook No. 4, dated
September 21, 1928, was published in 1928.
The individual parts of the NESC were published as NBS Handbook No. 6, February 5,
1926 — Part 1; NBS Handbook No. 7, March 12, 1926 — Part 3; NBS Handbook No. 8,
July 15, 1926 — Part 4; NBS Handbook No. 9, July 15, 1926 — Part 5; and NBS Handbook
No. 10, April 15, 1927 — Part 2.
1930’s and 1940’s: Also Active
The various parts of the NESC were revised separately by the sectional committee concept
following the procedures of the American Standards Association. The revisions were issued
as NBS Handbook H31 issued May 8, 1940 — Part 1; NBS Handbook H32 issued Septem-
ber 23, 1941 — Part 2; NBS Handbook H33 issued January 23, 1940 — Part 3; NBS Hand-
book H34 issued October 13, 1938 — Part 4; and NBS Handbook H35 issued December 1,
1939 — Part 5. NBS Handbook H39 issued July 15, 1944 was a discussion of the fifth
edition of Part 2 and the grounding rules.
A complete fifth edition with all five parts was issued in March of 1948 as NBS Handbook
H30. It combined Handbooks H31 to H35 inclusive under one cover. The page numbers of
the separate handbooks were retained to assist in the location of specific code rules regard-
less of the volume used.
Part 2 and the discussion of Part 2, definitions and grounding rules of the fifth edition, were
also issued August 15, 1949, as NBS Handbook H43.
Revisions of the 1950’s and 1960’s
Part 2, definitions and grounding rules, were reviewed for revision and updating starting in
the early 1950’s and issued November 1, 1961, as the Sixth Edition or NBS Handbook
No. 81. The IEEE started a new review of NESC with the purpose of complete upgrading in
1964. A working group was formed and called “Working Group Correlating Advances in
Technology in the Transmission and Disbribution Field with the National Electrical Safety
Code.” A large group, averaging 40 members of IEEE and ASCE, worked six years pro-
ducing a completely new updated draft of Part 2. This draft was forwarded to ANSI C2 and
formed the basis for revision of the Sixth Edition. Two supplements to Handbook H81 were
issued, one in December 15, 1965, and the second in March 1968.
Very Active 1970’s
In January 1970, the ANSI C2 Committee elected to start the revision of NESC, all parts.
Considerable activitity by all interested parties and organizations has continued to this
date.
Old Part 3, “Rules for the Installation and Maintenance of Electric Utilization Equipment,”
and Part 5, “Rules for Radio Installations,’’ were removed from the code in 1970. It was felt
that the rules for utilization equipment were now thoroughly covered by the National Elec-
trical Code and there was no further interest in the rules for radio installations. Late in
1972, the National Bureau of Standards acted to step out of the role as secretariat for the
American National Standards Committee C2 on the NESC. The Institute of Electrical and
Electronics Engineers (IEEE) was designated as the administrative secretariat. Part 1 was
revised July 1971 and issued as NBS Handbook 110.1 in June 1972.
The 1973 edition of the National Electrical Safety Code is dated July 20, 1973. It includes:
Section 9 — Rules covering methods of protective grounding of circuits, equipment, and
lightning arresters for stations, lines and utilization equipment (C2.2-1960).
Part 1 — Rules for the installation and maintenance of electrical supply stations and equip-
ment (C2.1-1971).
Part 2 — Safety rules for the installation and maintenance of electric supply and communi-
cation lines (C2.2-1960) and (C2.2a-1965).
Part 3 — Safety rules for the installation and maintenance of underground electrical supply
and communication lines (C2.3-1973). This supersedes Section 29 of C2.2-1960 and supple-
ment C2.2b-1967.
Part 4 — Rules for the operation of electric supply and communication lines and equipment
(C2.4-1973).
THE ANSI UMBRELLA
A review of the ANSI “voluntary consensus standards method” helps put into perspective
the long, long process in obtaining a new NESC.
The American National Standards Institute is a private, non-profit, voluntary organization
that has been in existence (under various names) for 57 years. It was formed in 1918 as the
American Engineering Standards Committee by five leading professional societies and three
agencies of the federal government. In structure, ANSI today is a federation of standards
competence having as its members some 175 professional, trade, technical, labor and con-
sumer organizations and 860 industrial or commercial firms. While the Institute has no
government members per se, several thousand officials representing federal, state and local
governments serve on ANSI committees, boards and councils as well as on standards devel-
oping groups using ANSI procedures. The Institute’s programs are financed by a combina-
tion of membership dues, special project support and the sale of American National Stan-
dards. Federal funding is provided on shared basis in support of some special projects, but
this source accounts for less than 1/4 of one percent of ANSI’s operating budget.
ANSI is governed by a Board of Directors with approximately one-third industrial-
commercial representatives, one-third technical-organizational representatives and one-third
public (government-consumer) representatives.
ANSI acts as the “focal point” for industrial standardization. Ninety percent of the stan-
dards in use are produced by approximately 12 to 15 major groups in the United States,
and all of them cooperate as members of the ANSI federation. Such participation is vital to
ANSI in order to identify work in progress and to have the ability to organize competence
to meet new standards needs. If ANSI did not exist, these standards developing groups
would quickly feel the need to establish a coordinating mechanism. If ANSI did not exist,
there would be no single standards approval process by which anyone’s standard might be
judged. There would instead be a dozen or more sets of standards, each with its own degree
of competence, credibility and participation. Without ANSI, a need for a single set of
national standards would be felt and perhaps filled by govenment.
ANSI’s Purpose
ANSI’s purpose is:
1. To serve as the national coordinating institution for voluntary standardization and
certification in the United States;
2. To assure appropriate representation and participation in standardization by the
public (including consumers and labor), industry and government;
3. To provide an effective means of determining the need for new standards, to
assure activity by existing organizations competent to resolve the need, and to
work toward establishment of suitable groups for these purposes where such do
not already exist;
4. To establish, promulgate and administer procedures and criteria for recognition
and approval of standards as American National (consensus) Standards;
5. To cooperate with departments and agencies of federal, state and local govern-
ments in achieving optimum compatibility between government codes and stan-
dards and the standards of industry and to promote optimum usage of Amercian
National Standards;
6. To represent the standards interest of the United States in international non-
treaty organizations with which ANSI is or may become affiliated;
7. To serve as a clearing-house for information on standards, standardization pro-
grams and certification.
Consensus Standards
ANSI provides within a single organization the basic elements essential to the recognition
of national consensus standards. ANSI’s approval procedures ensure a consensus of affected
interests. Its requirements for due process and the right to appeal actions at several levels
of review provide confidence in and credibility to its approved standards. In brief, ANSI is
the accepted voluntary system through which standards may be nationally recognized and
accepted, no matter what the origin.
Through full use of its completely independent approval procedures, which include full
public review and comment on all standards proposed for adoption as American National
Standards, ANSI provides the highest level of nationally recognized consensus of parties at
interest.
ANSI’s belief is that the best way to achieve national standards is by voluntary participation
of all concerned interests in the development of such standards and to ensure sufficiently
wide acceptance of its provisions, what ANSI calls consensus, so that the standard will be
used and will be the benefit to all.
ANSI’s national consensus implies general recognition and acceptance for use of a standard.
It ensures that parties having a substantial interest in the scope of provision of a given stan-
dard have been afforded an opportunity to participate in its development or to comment on
its provisions. All comments and negative positions must be given full and complete conside-
ration and resolution attempted to the satisfaction of the independent Board of Standards
Review, which, under the ANSI structure is responsible for approval of all American
National Standards as well as for revisions, reaffirmations or withdrawals.
Complete Board Review
The Board of Standards Review (BSR) consists of 14 individuals who are appointed to serve
because of their personal knowledge and experience in the standardization process and
their ability to review cases in an impartial and neutral manner. The BSR judges whether a
consensus exists for a standard on the basis of evidence submitted by the sponsor or secre-
tariat. There have been cases where approval of a standard was rejected because of a single
unresolved negative ballot from one important and concerned group with good substantive
reasons. On the other hand, the BSR approved standards that were submitted with several
unresolved negatives but that were considered unsubstantive or from groups not substan-
tially affected by the standard.
No one can afford duplication or conflict in standards. These problems can be avoided or
eliminated through ANSI control and consistency, which are essential elements in national
consensus standards. Through ANSI’s management and coordination of standards develop-
ment, both industry and government are assured that the manpower and resources provided
are properly and effectively utilized. Assignment of standards development responsibility
to outside organizations, under the jurisdiction of ANSI’s technical advisory boards (now
known as standards management boards), helps eliminate duplicate effort.
IEEE has the responsibility for ANSI C2, the National Electrical Safety Code.
ANSI Standards Methods
ANSI procedures provide for three basic methods by which American National Standards
may be developed and evidence of consensus submitted. One method is called the Canvass
Method. In this method a sponsor with a proprietary standard prepares a list of those having
substantial concern with the subject of the standard. The list is reviewed by the appropriate
Standards Management Board and additions are made if necessary. When the list is com-
pleted, the sponsor conducts a mail vote on the standard. The sponsor must attempt to
resolve objections. Finally, the Board of Standards Review exposes the standard to public
review and then examines the results of the canvass ballot, as well as the results of public
review.
The American National Standards Committee Method is another method provided for in
ANSI’s procedures. An American National Standards Committee is a semi-autonomous body
authorized and operating under the ANSI procedures with the administrative management
and techncial direction of an organziation willing to serve as secretariat. Such a committee
serves to review and vote on proposed Amercian National Standards submitted to it by
organizations that develop the standards. Where no appropriate body develops the stan-
dards, the American National Standards Committee may itself develop such standards.
The committee is open to all substantially concerned organizations that are willing to par-
ticipate. The secretariat is responsible for the classification of representatives for the pur-
pose of maintaining a balance between the various interests (for example, between pro-
ducers, consumers, distributors and general interests). As with the Canvass Method, the last
step is examination by ANSI’s Board of Standards Review.
Accredited Organization Method
This method was instituted when it became evident that some standards developing organi-
zations such as ASTM, NFPA and ASME utilzied procedures within their own organizations
that complied with ANSI’s basic requirements for participation by those substantially con-
cerned, maintaining a balance between various interests and so forth. It was redundant for
these organizations to be required by ANSI to use either the Canvass Method or the
American National Standards Committee Method, which were the only paths which ANSI
had for standards submittals.
The Accredited Organization Method permits direct submittals of standards to ANSI from
organizations that meet the ANSI criteria for accreditation. The principal requirements are
that the organization submit its operating procedures for the development of standards to
ANSI and that these procedures provide an opportunity for participation by all national
interests concerned: 1) balanced membership; 2) consideration of all objections to the
standard with the objective of resolution; and 3) a supervisory body to attest that the
organization’s procedures have been followed.
An accredited organization must keep ANSI advised regarding both standards work in pro-
gress and planned standards activities in order that ANSI may have adequate information
to manage and coordinate these activities in all standards developing organizations operating
in that area.
As with the Canvass Method and the American National Standards Committee Method,
standards submitted to ANSI under the Accredited Organization Method are subject to a
public review through announcement in ANSI’s Standards Action and approval by the
Board of Standards Review, based on the evidence of consensus.
1977 EDITION
When the decision was made in 1970 to revise Part 2 of NESC, five subcommittees were
formed:
Subcommittee 1 — Voltage Classifications and Clearances (Section 23).
Subcommittee 2 — Strength and Loadings (Sections 24, 25 and 26).
Subcommittee 3 — Grounding Methods (Section 9).
Subcommittee 4 — Insulation (Section 27).
Subcommittee 5 — Definitions, General and Miscellaneous (Sections A, 20, 21, 22 and
28).
These subcommittees had good representation throughout the 24 member organiza-
tions comprising the C2 Committee. Each subcommittee utilized the draft revision of
the Sixth Edition developed over a six year period by the IEEE Working Group Corre-
lating Advances in Technology in the Transmission and Distribution Field with NESC
as a basis for their initial revision considerations.
In May 1975, the C2 committee was reorganized into eight subcommittees to actively con-
sider all parts of the code:
SC1 Purpose, Scope, Application, and Definitions — Sections 1, 2
SC2 Grounding Methods — Section 9
SC3 Electric Supply Stations — Sections 10-19
SC4 Overhead Lines — Clearance — Section 23
SC5 Overhead Lines — Strength and Loading — Sections 24-26
SC6 Overhead Lines — General, Insulation and Miscellaneous — Sections 20, 22, 28
SC7 Underground Lines — Sections 30-32
SC8 Work Rules — Sections 40-44
The February 28, 1977 edition of NESC included the following:
Section 9 — Grounding methods for electric supply and communication facilities
(C2.2-1976).
Part 1 — Rules for the installation and maintenance of electric supply stations and
equipment (C2.1-1971).
Part 2 — Safety rules for the installation and maintenance of overhead supply and
communication lines (C2.2-1976).
Part 3 — Safety rules for the installation and maintenance of underground electric-
supply and communication lines (C2.3-1973).
Part 4 — Rules for operation of electric-supply and communication lines and equip-
ment (C2.4-1973).
10
1981 EDITION
The 1981 Edition of the National Electrical Safety Code, dated September 5, 1980, is the
result of continuing review by the subcommittees plus comments and suggestions of
interested parties.
As in 1913 and in all subsequent revisions, “SAFETY” has been the primary consideration
in the new National Electrical Safety Code, ANSI C2, 1981 Edition. As in the past, the
voluntary consensus standards methods of ANSI have again been thoroughly tested in
arriving at this new, advanced code edition.
Two new sections were introduced in the 1981 edition. Section 1 incorporates rules
common to all Parts and Section 2 consolidates all definitions into one location in the code.
These new Sections, 1 and 2, plus Section 9, Grounding Methods, are applicable to each of
the Parts 1, 2, 3, and 4.
The 1981 Edition includes the following:
Section 1 — Introduction to the National Electrical Safety Code
Section 2 — Definitions of special terms
Section 9 — Grounding methods for electric supply and communication facilities
Part 1 — Rules for the installation and maintenance of electric supply stations and
equipment.
Part 2 — Safety rules for the installation and maintenance of overhead supply and
communication lines.
Part 3 — Safety rules for the installation and maintenance of underground electric-
supply and communication lines.
Part 4 — Rules for the operation of electric-supply and communications lines and
equipment.
11
The former practice of designating parts by their edition has been eliminated. References to
the National Electrical Safety Code is now made by the year of the published volume and
the part number.
Interpretations Subcommittee
There is an active Interpretations Subcommittee reviewing, as requested, each application
for interpretation or clarification.
The topics requiring interpretation could be classified as (a) Covered in the Code, but not
clear; (b) Looking for support for Non-Code practices; (c) Situations not covered in the
Code; and (d) Topics probably covered but on which the Code is unclear in relation to a
specific situation.
A book, covering interpretation requests received and interpretations made during the years
1961 to 1977, was published by IEEE in 1978. The title of the book is ‘‘National Electrical
Safety Code Interpretations 1961-1977.”
SUMMARY
An extensive effort has been expended by a great number of people in arriving at a viable
and realistic NESC. The fundamental criteria considered were for safety and not design.
Design guides can be produced for specific conditions and situations. Minimum safety codes
require many different considerations by broadly experienced contributors.
As changes in technology occur on a continuing basis, it is desirable to recognize these
advancements in the Code standardization process. The development of realistic, practical
and useful codes requires continuing effort. The three-year cycle for revision on the
National Electrical Safety Code should help recognize these continuing advancements in
technology.
REFERENCES
1. ANSI C2 1981 Edition, published by the Institute of Electrical and Electronics
Engineers, 345 E. 47th Street, New York, NY.
12
ANSI C2 1977 and 1973 Editions published by IEEE.
ANSI Background from remarks by Mario A. Pisciotta at the Edison Electric
Institute Transmission & Distribution Committee Meeting, Minneapolis, Minne-
sota, May 9, 1975.
A Historical Development of NESC from material prepared by A. A. Chase,
Northeast Utilities Service Company, contributed to a panel discussion of IEEE,
January 28, 1975.
13
1984 NESC APPLICATION GUIDELINES
1984 NATIONAL ELECTRICAL SAFETY CODE
APPLICATION GUIDELINES
The following is a basic outline of the National Electrical Safety Code, 1984
Edition:
Section1 - Introduction
Section 2 - Definitions of Special Terms
Section 3 - List of Referenced Documents
Section 9 - Grounding Methods for Electric Supply and Communication
Facilities
Part 1 - Rules for the Installation and Maintenance of Electric Supply
Stations and Equipment
Part 2 - Safety Rules for the Installation and Maintenance of Overhead
Supply and Communication Lines
Part 3 - Safety Rules for the Installation and Maintenance of Under-
ground Electric-Supply and Communication Lines
Part 4 - Rules for the Operation of Electric-Supply and Communication
Lines and Equipment
Fundamental to the use of the Code is an understanding of Sections 1, 2 and 3
which are applicable to each of the Parts 1, 2, 3 and 4.
Section 1
The purpose of the rules is stated as the practical safeguarding of persons during
installation, operation, or maintenance of electric-supply and communication lines
and their associated equipment. They contain minimum provisions considered
necessary for the safety of employees and the public. They are not intended as a
design specification or an instruction manual.
14
Rule 011 indicates the rules cover supply and communication:
° lines
e equipment
° and associated work practices
employed by:
. electric supply utility
° communication utility
. railway utility
. or similar utility
in the exercise of its function as a utility. They cover similar systems under the control of
qualified persons, such as those associated with an industrial complex. The rules do not
cover:
° mines
° ships
° railway rolling equipment
¢ aircraft equipment
° automotive equipment
° utilization wiring (except as covered in Parts 1 and 3)
For all particulars not specified in the code, Rule 012 advises that construction and main-
tenance should be done in accordance with accepted good practice for the given local condi-
tions.
Rule 013 states that these rules shall apply to new installations and to extensions. Existing
installations including maintenance replacements which comply with prior editions of the
Code, need not be modified to comply with these rules except as may be required for safety
reasons by the administrative authority.
15
Rule 015 states that rules which are regarded as mandatory are characterized by the use of
the word “‘shall.”” Where a rule is of an advisory nature, to be followed insofar as practical,
it is indicated by the use of the word “should.” Other practices which are considered de-
sirable, but not intended to be mandatory, are stated as ‘“‘recommendations.”
Rule 016 states that unless otherwise stipulated by the administrative authority this code
shall become effective 180 days following the date of its publication.
Section 2
Many definitions of special terms are given in Section 2 and, for definitions not contained
therein, reference is made to ANSI/IEEE Std 100-1977, IEEE Standard Dictionary of
Electrical and Electronic Terms.
A working knowledge of these terms is necessary for interpretation of the Code. As an ex-
ample, the distinction between supply lines and communication lines is of prime impor-
tance:
Electric-Supply Lines (syn: supply lines) — Those conductors used to transmit electric
energy and their necessary supporting or containing structures. Signal lines of more
than 400 volts are always supply lines within the meaning of the rules, and those of
less than 400 volts may be considered as supply lines, if so run and operated through-
out.
Communication Lines — The conductors and their supporting or containing structures
which are used for public or private signal or communication service, and which
operate at potentials not exceeding 400 volts to ground or 750 volts between any two
points of the circuit, and the transmitted power of which does not exceed 150 watts.
When operating at less than 150 volts, no limit is placed on the transmitted power of
the system. Under specified conditions, communication cable may include communica-
tion circuits exceeding the preceding limitations where such circuits are also to supply
power solely to communication equipment.
Note: Telephone, telegraph, railroad-signal, data, clock, fire, police-alarms, cable
television and other systems conforming with the above are included. Lines
16
used for signaling purposes, but not included under the above definition, are
considered as supply lines of the same voltage and are to be so installed.
Another example is the distinction between a grounded conductor and a grounding con-
ductor:
Grounded Conductor — A conductor which is intentionally grounded, either solidly
or through a noninterrupting current-limiting device.
Grounding Conductor — A conductor which is used to connect the equipment or the
wiring system with a grounding electrode or electrodes.
Section 9
The basic outline of Section 9, Grounding Methods for Electric Supply and Communica-
tion Facilities, is as follows:
Rule 90 —
Rule 9] —
Rule 92 —
Rule 93 —
Rule 94 —
Rule 95 —
Rule 96 —
Rule 97 —
Rule 98 —
Rule 99 —
Purpose
Scope
Point of Connection of Grounding Conductor
Grounding Conductor and Means of Connection
Grounding Electrodes
Method of Connection to Electrode
Ground Resistance
Separation of Grounding Conductors
Rule 98 not used in this edition
Grounding Methods for Telephone and Other Communication Apparatus
on Circuits Exposed to Supply Lines or Lightning
Section 9 of the Code covers methods of protective grounding of supply and communica-
tion conductors and equipment. The rules requiring grounding are in Parts 1, 2, 3 and 4 of
the code.
Rule 92 covers requirements governing the point at which grounding connection is made to
the wiring system, fences, messenger wires and guys.
17
Rule 93 deals with the composition, ampacity, strength and protection of the grounding
conductor.
Grounding electrode requirements are covered in Rule 94 and include metallic water piping
systems, driven rods, buried wire, pole butt plates, wire raps, concrete-encased electrodes,
etc,
Rule 95 deals with connections made to the grounding electrode.
Rule 96 covers ground resistance requirements for supply stations and wiring systems.
Rule 97 presents conditions under which a grounding conductor must be run separately to
the grounding electrode as opposed to using a single common grounding conductor.
Requirements related specifically to grounding of telephone and other communication
apparatus are covered in Rule 99.
Part 1
The following is the basic outline of Part 1, Rules for the Installation and Maintenance of
Electric Supply Stations and Equipment:
Section 10 — Purpose and Scope of Rules
Section 11 — Protective Arrangements in Electric Supply Stations
Section 12 — Installation and Maintenance of Equipment
Section 13 — Rotating Equipment
Section 14 — Storage Batteries
Section 15 — Transformers and Regulators
Section 16 — Conductors
Section 17 — Circuit Breakers, Reclosers, Switches and Fuses
Section 18 — Switchgear and Metal Enclosed Bus
Section 19 — Surge Arresters
18
Rule 101 of Section 10 describes the scope as follows:
Part I of this code covers the electric supply conductors and equipment, along with
the associated structural arrangements in electric supply stations, which are accessible
only to qualified personnel. It also covers the conductors and equipment employed
primarily for the utilization of electric power when such conductors and equipment
are used by the utility in the exercise of its function as a utility.
Section 11 covers requirements relating to the use of rooms, fences, screens, etc., for the
enclosing of electric supply conductors and equipment. Illumination levels and emergency
lighting are also covered in this section along with requirements relating to floors, passage-
ways, stairs, exits and fire extinguishing equipment.
Requirements for inspection, guarding and work space about equipment are contained in
Section 12. Rule 124 contains clearance requirements for live parts. Also included in this
section are requirements concerning hazardous locations, such as coal-handling and boiler
areas, plus areas for the use and storage of flammable liquids, gases, etc.
Section 13 covers control requirements for rotating equipment.
The location, construction, illumination and ventilation requirements of areas for storage
batteries and requirements for storage battery service facilities are in Section 14.
Location and arrangement requirements of both indoor and outdoor installations of trans-
formers and regulators are covered in Section 15.
Section 16 provides rules governing mechanical and electrical protection in addition to ter-
mination of conductors.
The arrangement and application of circuit breakers, reclosers, switches and fuses are
covered in Section 17.
Requirements relating to switchgear, switchboards, motor control centers and metal en-
closed bus are contained in Section 18.
Section 19 covers requirements applying specifically to surge arresters.
19
Part 2
The basic outline of Part 2, Safety Rules for the Installation and Maintenance of Overhead
Supply and Communication Lines, is as follows:
Section 20 — Purpose, Scope and Application of Rules
Section 2] — General Requirements
Section 22 — Relations Between Various Classes of Lines
Section 23 — Clearances
Section 24 — Grades of Construction
Section 25 — Loading for Grades B, C, and D
Section 26 — Strength Requirements
Section 27 — Line Insulation
Section 28 — Miscellaneous Requirements
Part 2 of the Code covers supply and communication conductors and equipment in over-
head lines. It covers the associated structural arrangements and the extension of such
systems into buildings. Included are requirements for spacing, clearances, and strength
of construction. Part 2 does not cover installations in electric supply stations.
The general requirements for application given in Section 1, Rule 013, apply to Part 2.
However, when a structure is replaced, the arrangement of equipment shall conform to
Rule 238C covering clearances for span wires or brackets carrying luminaires or trolley
conductors.
Section 2] presents general requirements concerning accessibility, inspection and tests,
arrangement of switches and grounding. Rule 215 covers grounding requirements of neu-
trals, surge arresters and noncurrent-carrying parts such as guys, structures, equipment,
etc. Rule 215 also refers to Section 9 of the Code for rules covering methods of grounding.
While induced voltages are not covered in detail by the Code, Rule 212 recommends co-
operation between owners or operators of proximate facilities so that induced voltages are
controlled.
20
Section 22 deals with relations between various classes of lines. Rule 220B states that where
supply and communication conductors cross each other or are located on the same struc-
tures, the supply conductors should be carried at the higher level. Exceptions covered in
this rule are trolley feeders and supply circuits of 600 volts or less and carrying power not
in excess of 5 kW.
Rule 220C covers relative levels of supply lines of different voltage classifications (as clas-
sified in Table 235-5). These voltage levels are:
0 to 750 volts plus
Supply cables meeting Rule 230C1, 2 or 3
Neutral conductors meeting Rule 230E1
750 to 8.7kV
8.7kV to 15 kV
15 kV to S0kV
At crossings, the higher voltage line should be carried at the higher level. The same should
apply on structures where all circuits are owned by one utility. On structures with circuits
owned by separate utilities, Rule 220C2b provides for grouping of the circuits of each
utility and states the specific requirements to be met.
Section 23 covers all clearances, including climbing space involving overhead supply and
communication lines. However, clearances of equipment from structure surfaces, from
spaces accessible to the general public, and height above ground are covered in Section 28.
A generalized grouping of the rules in Section 23 is as follows:
Rule 231 Clearances of supporting structures from fire hydrants, streets,
roads, highways and railroad tracks.
Rules 232 to 234 Clearances of wires, conductors and cables over or horizontally
from other installations or objects.
Rules 235 to 239 Clearances and spacings on the supporting structure.
2
A number of the clearance requirements are dependent on the wire, conductor or cable
size, sag, and span length.
Section 24 specifies construction grades on the basis of the required strengths for safety.
Four grades are used, and the relative order from highest to lowest is B, C, D, and N. Grade
D, however, is only specified for communication lines. Basically, the grade is determined
on the basis of the type of conductor and what is below the conductor. Table 242-1 applies
to supply conductors, and Table 242-2 applies to communication conductors. Table 241-1
applies to communication conductors for the specific case where they cross over supply
conductors and railroad tracks in the same span.
To demonstrate the use of these tables, assume a 13.2 kV open conductor supply line is
to be built on public rights-of-way through both urban and rural areas and crosses over rail-
road tracks and limited access highways only. The line to ground voltage for the circuit is
7.62 kV. From Table 242-1, we find the required grades to be:
Construction
Grade
Public Rights-of-way (Rural) N
Public Rights-of-way (Urban) Gc
Railroad tracks and limited access highways B
These would be the minimum construction grades required. It is left to the engineer to
determine how many designs are to be used to satisfy these requirements. In general, the
alternatives are:
1. Three designs with each based on a different grade of construction.
2. Two designs with one based on Grade B and the other based on either C or N.
3. One design based on Grade B.
Rules 243A and 243B state that the grade of construction for structures, crossarms and
support arms shall be that required for the highest grade of conductors carried by them,
except for a few modifications listed in the two rules. Rule 243C states that pins, armless
construction brackets, insulators, and conductor fastenings shall have the grade of con-
struction required for the conductor concerned, except for the modification list in the rule.
22
Section 25 provides minimum loading to be used for construction Grades B, C, and D. Two
types of loading are specified, namely, combined ice and wind loading and extreme wind
loading. Figure 250-1 provides a map of the United States showing the combined ice and
wind loading districts, termed Heavy, Medium, and Light. Table 250-1 shows the minimum
radial thickness of ice and wind pressure to be used in each of the loading districts. Figure
250-2 also presents a map of the United States and shows the minimum wind pressures to
be used for calculating loads upon tall structures. The wind pressure to be used at a specific
location shall not be less than that of the nearest pressure line shown on Figure 250-2.
Rule 251-1B discusses the vertical and horizontal components of conductor loading. It
further defines total loading as the resultant of these components, to which resultant has
been added the constant specified in Table 251-1. In all cases, the conductor tension shall
be computed from this total loading at the temperature that is also specified in Table 251-1.
Rule 252 discusses these loadings in relation to support loads.
The Code does not specify minimum loading for Grade N construction.
Section 26 deals with the strength requirement of the various components of construction,
such as:
¢ — Structures
. Foundations
e Guys and Guy Anchors
¢ — Crossarms
° Conductors and Cables
The requirements for construction Grades B and C are covered in Rule 261. Construction
Grades D and N are covered by Rules 262 and 263, respectively. Overload capacity factors
are specified for the various support facilities and apply to the loadings that were covered in
Section 25.
Of primary importance to the use of Part 2 is the knowledge that conductor and cable
minimum sizes and tension limitations are specified in Section 26. The requirements are
found in the rules as follows:
23
Rules 261H thru 261L for Grades B and C
Rules 262H and 262I for Grade D
Rules 263D and 263G for Grade N
Section 27 covers insulation level and mechanical strength requirements and refers to many
applicable American National Standards. This section applies to open conductor supply
lines.
Miscellaneous requirements are covered in Section 28, such as:
Rule 280 — Structures
Rule 281 — Tree Trimming
Rule 282 — Guying and Bracing
Rule 283 — Insulator in Guys
Rule 284 — Span-Wire Insulators
Rule 285 — Overhead Conductors
Rule 286 — Equipment on Supporting Structures
Rule 287 — Communications Protective Requirements
Rule 288 — Circuits of One Class Used in the Operation of Circuits of Another Class
Rule 289 — Electric Railway Construction
Part 3
The following is a basic outline of Part 3, Safety Rules for the Installation and Mainte-
nance of Underground Electric-Supply and Communication Lines:
Section 30 — Purpose, Scope and Application of Rules
Section 31 — General Requirements Applying to Underground Lines
Section 32 — Underground Conduit Systems
Section 33 — Supply Cable
Section 34 — Cable in Underground Structures
Section 35 — Direct Buried Cable
Section 36 — Risers
24
Section 37 — Supply Cable Terminations
Section 38 — Equipment
Section 39 — Installation in Tunnels
Rule 301 of Section 30 describes the scope as follows:
Part 3 of this code covers supply and communication cables and equipment in under-
ground or buried systems. The rules cover the associated structural arrangements and
the extension of such systems into buildings. It also covers the cables and equipment
employed primarily for the utilization of electric power when such cables and equip-
ment are used by the utility in the exercise of its function as a utility. They do not
cover installations in electric supply stations.
Section 31 gives general requirements applying to underground lines. These requirements
concern installation, maintenance, accessibility, inspection and tests, grounding, communi-
cation apparatus protection and elimination of induced voltages.
Section 32, dealing with underground conduit systems, starts with a note that repeats de-
finitions from Section 2 which are particularly important to the interpretation of this part
of the code. These definitions are:
Duct — A single enclosed raceway for conductors or cable.
Conduit — A structure containing one or more ducts.
Conduit System — The combination of conduit, conduits, manholes, and vaults
joined to form an integrated whole.
The following three definitions from Section 2 are also germane to an understanding of
Part 3:
Vault — An enclosure above or below ground which personnel may enter
and is used for the purpose of installing, operating, or maintain-
ing equipment which need not be of a submersible design.
25
Manhole — A subsurface enclosure which personnel may enter and which is
used for the purpose of installing, operating and maintaining sub-
mersible equipment and cable.
Handhole — An access opening, provided in equipment or in a below-the-
surface enclosure in connection with underground lines, into
which men reach but do not enter, for the purpose of installing,
operating, or maintaining equipment or cable or both.
Rule 320 of Section 32 deals with routing of the conduit system and clearances from
other underground installations. The requirements for routing cover such things as natural
hazards, highways, streets, bridges, tunnels, railroad track crossings and submarine crossings.
The clearance requirements relate to such facilities as sewers, water lines, fuel lines, steam
lines and the separation between supply and communication conduit systems.
Requirements dealing with excavation and backfill are covered in Rule 32] with ducts and
their joints covered in Rule 322.
Rule 323 of Section 32 contains requirements such as strength, dimensions, access, drainage
and ventilation for manholes, handholes, and vaults.
Section 33 provides supply cable requirements that include sheaths, jackets and shielding.
Also included in this section are requirements related to cable accessories and joints. This
section applies to supply cables to be installed in an underground conduit system as well as
to direct buried cable.
Section 34 deals with cable in underground structures. The requirements in this section
cover installation of cables along with supports and clearances in manholes and vaults.
Other requirements included in this section concern grounding and bonding, plus require-
ments concerned with communication cables that contain special supply circuits.
Section 35 provides routing, clearance from other underground structure and installation
requirements for direct buried cable.
Rules applying to risers are contained in Section 36 and include both pole risers and risers
to pad-mounted installations.
26
Requirements related to clearances, grounding and support of supply cable terminations are
covered in Section 37.
Section 38 contains rules applying to both electric-supply and communication equipment.
The rules cover design, location within underground structures, installation and grounding
of equipment.
Section 39 provides supplemental or modification rules for the installation of supply and
communication facilities in tunnels.
Part 4
The basic outline of Part 4, Rules for the Operation of Electric-Supply and Communica-
tion Lines and Equipment, is as follows:
Section A — Reference to Other Standards
Section 40 — Purpose and Scope
Section 41 — Supply and Communications Systems — Rules for Employers
Section 42 — Supply Systems — Rules for Employees
Section 43 — Communications Systems — Rules for Employees
Section A references American National Standards which should be used in conjunction
with Part 4 of the Code.
Rule 401 of Section 40 describes the scope as follows:
Part 4 of this code covers work rules to be followed in the installation, operation and
maintenance of electric supply and communication systems.
Section 41 applies to both supply and communication systems and covers rules for the
employer. These rules deal with such subjects as safety rules, emergency procedures, first
aid rules, designation of responsibility, protective methods, protective devices and inspec-
tion and tests of protective devices. Essentially, this section requires that employees receive
instruction on these subjects and follow up supervision to ensure that rules, procedures
and methods are followed.
27
Section 42 covers rules for supply system employees. Rule 420 deals with general precau-
tions, while Rule 42] handles operating routines.
Rule 422 contains requirements concerned with the handling of energized equipment or
lines. This rule covers clearances to be maintained by employees from live parts and require-
ments relating to switches, capacitors, current transformers, connections, working posi-
tion, etc.
Procedures and methods for de-energizing equipment or lines and the restoration of service
is covered in Rule 423.
Rule 424 contains requirements applying to the installation and removal of protective
grounds.
Rules 425 and 426 provide added requirements related specifically to work on overhead
lines and underground lines, respectively.
Additional requirements for bare-hand live line work, including training, equipment, bond-
ing, shielding and clearances, are covered by Rule 427.
Section 43 contains rules for communications systems employees. The general precautions
and operating routines are covered by Rules 430 and 431, respectively. Rules 432 and 433
present additional requirements applying to work on overhead lines and underground lines,
respectively.
28
CHANGES TO THE 1981 NESC
1984 Revisions to the NESC
Key: Werds-deleted (_—______)
Words added (underderlined)
RULE 013A 1984 EDITION
NEW INSTALLATIONS AND EXTENSIONS
1. THESE RULES SHALL APPLY TO ALL NEW INSTALLATIONS AND EXTENSIONS, EXCEPT THAT THEY MAY BE WAIVED OR MODIFIED BY THE ADMINISTRATIVE AUTHORITY. WHEN SO WAIVED OR MODIFIED EQUIVALENT -6R—GREATER SAFETY SHALL BE PROVIDED IN OTHER WAYS, INCLUDING SPECIAL WORKING MEHTODS.
RULE 016 1984 EDITION
EFFECTIVE DATE
UNLESS OTHERWISE STIPULATED BY THE ADMINISTRATIVE AUTHORITY, THIS CODE SHALL BECOME EFFECTIVE 180 DAYS FOLLOWING THE DATE OF ITS PUBLICATION AND SHALL APPLY TO NEW INSTALLATIONS AND EXTENSIONS WHERE BOTH DESIGN AND APPROVAL WERE STARTED AFTER THE EXPIRATION OF THAT PERIOD.
RULE 017 1984 EDITION
UNITS OF MEASURE
ADD METRIC UNITS TO NESC.
NESC Seminar/Misc.
SECTION 2
SECTION 2
SECTION 2
SECTION 2
DEFINITIONS 1981 EDITION
CONDUCTOR NO. 8
LINE CONDUCTOR. A CONDUCTOR INTENDED TO CARRY ELECTRIC CURRENTS,
SUPPORTED BY POLES, TOWERS, OR OTHER STRUCTURES, BUT NOT INCLUDING
VERTICAL OR LATERAL CONDUCTORS.
DEFINTIONS 1984 EDITION
CONDUCTOR NO. 8
LINE CONDUCTOR. (OVERHEAD SUPPLY OR COMMUNICATION LINES). A WIRE OR
CABLE INTENDED TO CARRY ELECTRIC CURRENTS, EXTENDING ALONG THE ROUTE OF
THE LINE, SUPPORTED BY POLES, TOWERS OR OTHER STRUCTURES, BUT NOT
INCLUDING VERTICAL OR LATERAL CONDUCTORS.
NEW DEFINITION 1984 EDITION
DESIGNATED PERSON. A QUALIFIED PERSON DESIGNATED TO PERFORM SPECIFIC
DUTIES UNDER THE CONDITIONS EXISTING. SYN: DESIGNATED EMPLOYEE.
DEFINITIONS 1984 EDITION
ELECTRIC SUPPLY STATION. ANY BUILDING, ROOM, OR SEPARATE SPACE WITHIN
WHICH ELECTRIC SUPPLY EQUIPMENT IS LOCATED AND THE INTERIOR OF WHICH IS
ACCESSIBLE, AS A RULE, ONLY TO QUALIFIED PERSONS. THIS INCLUDES
GENERATING STATIONS AND SUBSTATIONS, INCLUDING THEIR ASSOCIATED
GENERATOR, STORAGE BATTERY, TRANSFORMER AND SWITCHGEAR ROOMS OR
ENCLOSURES BUT DOES NOT INCLUDE FACILITIES SUCH AS PAD MOUNTED EQUIPMENT
AND INSTALLATIONS IN MANHOLES AND VAULTS.
NESC Seminar/Mi eer,
SECTION 2 DEFINITIONS 1981 EDITION
PAD MOUNTED. A METHOD OF SUPPORTING EQUIPMENT, GENERALLY AT GROUND
LEVEL.
SECTION 2 DEFINITIONS 1984 EDITION
PAD MOUNTED EQUIPMENT. A GENERAL TERM DESCRIBING ENCLOSED EQUIPMENT, THE
EXTERIOR OF WHICH ENCLOSURE IS AT GROUND POTENTIAL, POSITIONED ON A
SURFACE-MOUNTED PAD.
SECTION 2 DEFINITIONS 1981 EDITION
SECTION 2 DEFINITIONS 1984 EDITION
UTILITY INTERACTIVE SYSTEM. AN ELECTRIC POWER PRODUCTION SYSTEM WHICH IS
OPERATING IN PARALLEL WITH AND CAPABLE OF DELIVERING ENERGY TO A UTILITY
ELECTRIC SUPPLY SYSTEM.
SECTION 3. LIST OF REFERENCED DOCUMENTS 1984 EDITION
NEW SECTION
NESC Seminar/Misc.
RULE 92B
RULE 97D
1984 EDITION
750 VOLTS AND BELOW
THE POINT OF GROUNDING CONNECTION ON THREE-PHASE THREE-WIRE SYSTEM, WHETHER DERIVED FROM A DELTA CONNECTED OR AN UNGROUNDED WIRE CONNECTED TRANSFORMER INSTALLATION NOT USED FOR LIGHTING, MAY BE ANY OF THE CIRCUIT CONDUCTORS, OR IT MAY BE A SEPARATELY DERIVED NEUTRAL.
1984 EDITION
UNGROUNDED OR SINGLE GROUNDED SYSTEMS
WHERE THE SECONDARY NEUTRAL IS NOT INTERCONNECTED WITH THE PRIMARY SURGE ARRESTER GROUNDING CONDUCTOR AS IN RULE 97B, INTERCONNECTION MAY BE MADE THROUGH A SPARK GAP OR DEVICE WHICH PERFORMS AN EQUIVALENT FUNCTION. THE GAP OR DEVICE SHALL HAVE A 60 HZ BREAKDOWN VOLTAGE OF AT LEAST TWICE THE PRIMARY CIRCUIT VOLTAGE BUT NOT NECESSARILY MORE THAN 10KV. AT LEAST ONE OTHER GROUNDING CONNECTION ON THE SECONDARY NEUTRAL SHALL BE PROVIDED WITH ITS GROUNDING ELECTRODE LOCATED AT A DISTANCE OF NOT LESS THAN 20 FT. (6.1m) FROM THE SURGE ARRESTER GROUNDING ELECTRODE IN ADDITION TO CUSTOMERS’ GROUNDS AT EACH SERVICE ENTRANCE.
NESC Seminar/Misc.
RULE 97D
RULE 110A
1984 EDITION
MULTIPLE GROUNDED SYSTEMS
ON MULTIPLE GROUNDED SYSTEMS THE PRIMARY AND SECONDARY NEUTRALS SHOULD BE
INTERCONNECTED ACCORDING TO RULE
SEPARATE THE NEUTRALS, INTERCO CTIO! OF THE IE
THE GAP_OR DEVICE SHALL HAVE A 60 HZ BREAKDOWN VOLTAGE NOT EXCEEDING
3 KV. AT LEAST ONE OTHER GROUNDING CONNECTION ON THE SECONDARY NEUTRAL
SHALL BE PROVIDED WITH ITS GROUNDING ELECTRODE LOCATED AT A DISTANCE NOT
LESS THAN 6 FT. (1.8m) FROM THE PRIMARY NEUTRAL AND SURGE ARRESTER
GROUNDING ELECTRODE IN ADDITION TO THE CUSTOMER'S GROUNDS AT EACH SERVICE
ENTRANCE. SINCE A DIFFERENT POTENTIAL CAN EXIST WHERE PRIMARY AND
SECONDARY NEUTRALS ARE NOT DIRECTLY INTERCONNECTED THE SECONDARY
GROUNDING CONDUCTOR SHALL BE INSULATED FOR 600 VOLTS.
1984 EDITION
ENCLOSURE OF EQUIPMENT
METAL FENCES WHEN USED TO ENCLOSE ELECTRIC SUPPLY STATIONS HAVING
ENERGIZED ELECTRICAL CONDUCTORS OR EQUIPMENT SHALL HAVE A MINIMUM HEIGHT
OF SEVEN FEET (2.1m) OVERALL AND SHALL BE GROUNDED IN ACCORDANCE WITH
SECTION 9.
THE REQUIREMENTS FOR FENCE HEIGHT MAY BE SATISFIED WITH ANY ONE OF THE FOLLOWING:
1. FENCE FABRIC, SEVEN FEET (2.1m) OR MORE IN HEIGHT.
2. A COMBINATION OF SIX FEET (1.8m) OR MORE OF FENCE FABRIC AND A ONE-FOOT (300mm) EXTENSION UTILIZING THREE OR MORE STRANDS OF BARBED WIRE.
3. OTHER TYPES OF CONSTRUCTION, SUCH AS NONMETALLIC MATERIAL,
WHICH PRESENT EQUIVALENT BARRIERS TO CLIMBING OR OTHER
UNAUTHORIZED ENTRY.
NESC Seminar/Misc.
RULE 110C
RULE 110C
RULE 111E
RULE 111E
1981 EDITION
ELECTRIC EQUIPMENT
ALL STATIONARY EQUIPMENT SHALL BE SUPPORTED AND SECURED IN PLACE.
1984 EDITION
ELECTRIC EQUIPMENT
TO MINIMIZE MOVEMENTS ALL STATIONARY EQUIPMENT SHALL BE SUPPORTED AND
SECURED IN PLACE IN A MANNER CONSISTENT WITH ITS CONDITIONS OF SERVICE.
NOTE: IN AREAS OF LIMITED SEISMIC ACTIVITY, SOME EQUIPMENT, SUCH AS
TRANSFORMERS, MAYBE CONSIDERED AS SECURED IN PLACE BY THEIR OWN WEIGHT;
EQUIPMENT WHICH TENDS TO MOVE DURING OPERATION, SUCH AS CIRCUIT BREAKERS
AND ROTATING EQUIPMENT, ARE CONSIDERED TO REQUIRE APPRORPIATE ADDITIONAL
MEASURES.
1981 EDITION
RECEPTACLES IN DAMP OR WET LOCATIONS
ALL 120 V AC RECEPTACLE CIRCUITS SHALL EITHER BE PROVIDED WITH GROUND
FAULT CIRCUIT INTERRUPTER (GFI) PROTECTION, OR BE ON A GROUNDED CIRCUIT
WHICH IS PERIODICALLY TESTED.
1984 EDITION
RECEPTACLES IN DAMP OR WET LOCATIONS
ALL 120 V AC PERMANENT RECEPTACLES SHALL EITHER BE PROVIDED WITH GROUND FAULT INTERRUPTER (GFI) PROTECTION, OR BE ON A GROUNDED CIRCUIT WHICH IS TESTED AT SUCH INTERVALS AS EXPERIENCE HAS SHOWN TO BE NECESSARY.
NESC Seminar/Misc.
RULE 113A
RULE 113A
1981 EDITION
CLEAR EXISTS
EACH ROOM OR SPACE AND EACH WORKING SPACE ABOUT EQUIPMENT SHALL HAVE A
MEANS OF EXIT WHICH SHALL BE KEPT CLEAR OF ALL OBSTRUCTIONS. EXIST DOORS
SHALL BE EQUIPPED WITH LOCKS OR LATCHES THAT PERMIT OPENING BY MEANS OF
SIMPLE PRESSURE OR TORQUE ON THE ACTUATING PARTS UNDER ANY CONDITION.
1984 EDITION
CLEAR EXITS
EACH ROOM OR SPACE AND EACH WORKING SPACE ABOUT EQUIPMENT SHALL HAVE A MEANS OF EXIT WHICH SHALL BE KEPT CLEAR OF ALL OBSTRUCTIONS. EXIT DOORS SHALL SWING OUT AND BE EQUIPPED WITH PANIC BARS, PRESSURE PLATES OR OTHER
DEVICES THAT ARE NORMALLY LATCHED BUT OPEN UNDER SIMPLE PRESSURE.
EXCEPTION: THIS RULE DOES NOT APPLY TO EXISTS—IN—CONTROLHOUSES—AND GONFROL-ROOMS-OR-TO-GATES IN FENCES FOR OUTDOOR EQUIPMENT INSTALLATIONS.
NESC Seminar/Misc.
RULE 121A
RULE 121A
RULE 121B
RULE 121B
1981 EDITION
IN-SERVICE EQUIPMENT
ELECTRIC EQUIPMENT SHALL BE PERIODICALLY INSPECTED AND MAINTAINED.
DEFECTIVE EQUIPMENT OR WIRING SHALL BE PUT IN GOOD ORDER OR PERMANENTLY
DISCONNECTED.
1984 EDITION
IN-SERVICE EQUIPMENT
ELECTRIC EQUIPMENT SHALL BE INSPECTED AND MAINTAINED AT SUCH INTERVALS AS EXPERIENCE HAS SHOWN TO BE NECESSARY. EQUIPMENT OR WIRING FOUND TO BE DEFECTIVE SHALL BE PUT IN GOOD ORDER OR PERMANENTLY DISCONNECTED.
1981 EDITION
IDLE EQUIPMENT
INFREQUENTLY USED EQUIPMENT OR WIRING SHALL BE INSPECTED AND TESTED
BEFORE USE TO DETERMINE ITS FITNESS FOR SERVICE. IDLE EQUIPMENT
ENERGIZED BUT NOT CONNECTED TO LOAD SHALL BE INSPECTED OR MAINTAINED PERIODICALLY.
1984 EDITION
IDLE EQUIPMENT
INFREQUENTLY USED EQUIPMENT OR WIRING SHALL BE INSPECTED AND TESTED BEFORE USE TO DETERMINE ITS FITNESS FOR SERVICE. IDLE EQUIPMENT ENERGIZED BUT NOT CONNECTED TO A LOAD SHALL BE INSPECTED AND MAINTAINED AT SUCH INTERVALS AS EXPERIENCE HAS SHOWN TO BE NECESSARY.
NESC Seminar/Micr,
RULE 121C
RULE 121C
RULE 127
RULE 127
1981 EDITION
EMERGENCY EQUIPMENT
EQUIPMENT OR WIRING MAINTAINED FOR EMERGENCY SERVICE SHALL BE
PERIODICALLY INSPECTED AND TESTED TO DETERMINE ITS FITNESS FOR SERVICE.
1984 EDITION
EMERGENCY EQUIPMENT
EQUIPMENT AND WIRING MAINTAINED FOR EMERGENCY SERVICE SHALL BE INSPECTED
AND TESTED AT SUCH INTERVALS AS EXPERIENCE HAS SHOWN TO BE NECESSARY TO
DETERMINE ITS FITNESS FOR SERVICES.
1981 EDITION
CLASSIFIED LOCATIONS
ELECTRICAL INSTALLATIONS, IN HAZARDOUS AREAS SHALL MEET THE REQUIREMENTS
OF ARTICLES 500 THROUGH 503, AND ARTICLES 511 THROUGH 517 OF NFPA-78, THE
NATIONAL ELECTRICAL CODE.
1984 EDITION
CLASSIFIED LOCATIONS
ELECTRICAL INSTALLATIONS IN CLASSIFIED AREAS SHALL MEET THE REQUIREMENTS
OF ANSI/NFPA 70, NATIONAL ELECTRICAL CODE (NEC), ARTICLES 500 THRU 503
AND ARTICLES 511 THRU 517. (SEE NESC SECTION 3.)
NESC Seminar/Misc.
RULE 127A
RULE 127A
7.
RULE 146A
1984 EDITION
COAL-HANDLING AREAS
UNVENTILATED TUNNELS BELOW STOCKPILES OR SURGE PILES AND SPACE IDE, ABOVE OR BELOW COAL STORAGE SI OTHER ENCLOSED COAL STORAGE SPACES WHERE METHANE OR COAL DUST MAY ACCUMLATE, ARE CLASS I, DIVISION 1, GROUP D, AND CLASS II, DIVISION 1, GROUP F LOCATIONS.
1984 EDITION
ENCLOSED SECTIONS WHERE ONLY WET COAL IS HANDLED OR ENCLOSED SECTIONS SO
CUT OFF AS TO BE FREE FROM DANGEROUS AMOUNTS OF COAL DUST ARE NOT
CLASSIFIED. COAL SHALL BE CONSIDERED TO BE WET IF ENOUGH WATER SPRAYS
ARE INSTALLED AND MAINTAINED TO PREVENT MORE THAN 0.3 OUNCE (.85g) OF
COAL DUST PER CU. FT. (.028 cu m) OF ENCLOSED AIR VOLUME FROM BEING
THROWN INTO SUSPENSION OR FROM ACCUMULATING ON OR IN_ ELECTRICAL
EQUIPMENT.
1981 EDITION
PROPER EYE PROTECTION AND CLOTHING SHALL BE PROVIDED IN THE BATTERY AREA
DURING BATTERY MAINTENANCE AND INSTALLATION AND SHALL CONSIST OF:
GOGGLES OR FACE SHIELD
ACID RESISTANT GLOVES
PROTECTIVE APRONS AND OVERSHOES
PORTABLE OR STATIONARY WATER FACILITIES FOR RINSING EYES AND
SKIN.
-5.—_NEUTRALIZING—AGENT, Pwne eee NESC Seminar/Misc.
RULE 147 1981 EDITION
-£I—-IS— RECOMMENDED—THAT—THE— BATTER ¥Y— €HARGER——AND—ASSOCEATED—€ONTROL
EQUEPMENT—BE—LO€ATED—OUTSEDE A BATTERY ROOM OR AWAY FROMTHE —VECINE FY—-OF
—A- BATTERY AREA.
RULE 147 1984 EDITION
RULE 147 NOT USED IN THIS EDITION.
RULE 180A 1981 EDITION
GENERAL REQUIREMENTS FOR ALL SWITCHGEAR
1. SWITCHGEAR SHALL BE ANCHORED TO MINIMIZE MOVEMENT.
RULE 180A 1984 EDITION
GENERAL REQUIREMENTS FOR ALL SWITCHGEAR
1. TO MINIMIZE MOVEMENT, ALL SWITCHGEAR SHALL BE SECURED IN A MANNER CON-
SISTENT WITH ITS CONDITIONS OF SERVICE AND APPLICABLE MANUFACTURERS'
INSTRUCTIONS.
NESC Seminar/Misc.
RULE 180A
6.
RULE 180A
7.
RULE 180B
1.
1981 EDITION
1981 EDITION
1984 EDITION
SWITCHGEAR SHALL NOT BE LOCATED WITHIN 25 FT. (7.6m) HORIZONTALLY INDOORS OR 10 FT. (3.0m) OUTDOORS OF STORAGE CONTAINERS, VESSELS, UTILIZATION EQUIPMENT OR DEVICES CONTAINING FLAMMABLE LIQUIDS OR GASES.
EXCEPTION: IF AN INTERVENING BARRIER, DESIGNED TO MITIGATE THE POTENTIAL
EFFECTS OF FLAMMABLE LIQUIDS OR GASES, IS INSTALLED, THE DISTANCES LISTED
ABOVE DO NOT APPLY.
THE RESTRICTIONS ARE NOT INTENDED TO APPLY TO THE POWER TRANSFORMER(S) SUPPLYING THE SWITCHGEAR.
NESC Seminar/Misc,
RULE 180B
2.
RULE 180B
2.
RULE 180B
7.
RULE 180B
13.
1981 EDITION
ENCLOSED SWITCHGEAR ROOMS SHALL HAVE AT LEAST TWO MEANS OF EGRESS, ONE AT
EACH EXTREME OF THE AREA, NOT NECESSARILY IN OPPOSITE WALLS. DOORS SHALL
SWING OUT AND BE EQUIPPED WITH LOCKS OR LATCHES THAT PERMIT OPENING BY
MEANS OF SIMPLE PRESSURE OR TORQUE ON THE ACTUATING PARTS UNDER ANY
CONDITION.
1984 EDITION
ENCLOSED SWITCHGEAR ROOMS SHALL HAVE AT LEAST TWO MEANS OF EGRESS, ONE AT EACH EXTREME OF THE AREA, NOT NECESSARILY IN OPPOSITE WALLS. DOORS SHALL SWING OUT AND BE EQUIPPED WITH PANIC BARS, PRESSURE PLATES OR OTHER DEVICES THAT ARE NORMALLY LATCHED BUT OPEN UNDER SIMPLE PRESSURE.
EXCEPTION: ONE DOOR MAY BE USED WHEN REQUIRED BY PHYSICAL LIMITATIONS IF
MEANS ARE PROVIDED FOR UNHAMPERED EXIT DURING EMERGENCIES.
1984 EDITION
LOW-VOLTAGE CABLES OR CONDUCTORS, EXCEPT THOSE TO BE CONNECTED TO EQUIP-
MENT WITHIN THE COMPARTMENT, SHALL NOT BE ROUTED THROUGH THE MEDIUM - OR HIGH-VOLTAGE DIVISIONS OF SWITCHGEAR UNLESS INSTALLED IN RIGID METAL
CONDUIT OR ISOLATED BY RIGID METAL BARRIERS.
1981 EDITION
NESC Seminar/Misc.
RULE 181B
5.
RULE 210
RULE 210
RULE 211
RULE 230C
1981 EDITION
THE-~GENERATOR—45: Hi
ONE— ‘POINT -ONL¥.-- ENCLOSURES OF BUS AND ACCESSORTES SUCH AS POTENTEAL
‘TRANSFORMER:
GROUNDENG—EQUEPME
70 CARRY THE -BUS-MOMENFARY_GURRENT-BATING_POR—TWO-SECONDS.
1981 EDITION
RULE 210 NOT USED IN THIS EDITION.
1984 EDITION
REFERENCED SECTIONS
THE INTRODUCTION (SECTION 1), DEFINITIONS (SECTION 2), LIST OF REFERENCED DOCUMENTS (SECTION 3) AND GROUNDING METHODS (SECTION 9) SHALL APPLY TO
THE REQUIREMENTS OF PART 2.
1984 EDITION
THIS NUMBER IS NOT USED IN THIS EDITION.
1984 EDITION
SUPPLY CABLES
FOR CLEARANCE PURPOSES, SUPPLY CABLES, INCLUDING SPLICES AND TAPS,
CONFORMING TO ANY OF THE FOLLOWING REQUIREMENTS MAY BE PERMITTED LESSER
CLEARANCES THAN OPEN CONDUCTORS OF THE SAME VOLTAGE. CABLES SHOULD BE
CAPABLE OF WITHSTANDING TESTS APPLIED IN ACCORDANCE WITH AN APPLICABLE
STANDARD.
NES“ -Semi--</Mi--
RULE 230D
RULE 231B
1.
1984 EDITION
COVERED CONDUCTORS
COVERED CONDUCTORS SHALL BE CONSIDERED BARE CONDUCTORS FOR ALL CLEARANCE
REQUIREMENTS EXCEPT THAT SPACING BETWEEN CONDUCTORS OF THE SAME OR
DIFFERENT CIRCUITS, INCLUDING GROUNDED CONDUCTORS, MAY BE REDUCED BELOW
THE MINIMUM REQUIREMENTS FOR OPEN CONDUCTORS WHEN THE CONDUCTORS ARE
OWNED, OPERATED, OR MAINTAINED BY THE SAME PARTY AND WHEN THE CONDUCTOR
COVERING PROVIDES SUFFICIENT DIELECTRIC STRENGTH TO PREVENT A_ SHORT
CIRCUIT IN CASE OF MOMENTARY CONTACT BETWEEN CONDUCTORS OR BETWEEN
CONDUCTORS AND THE GROUNDED CONDUCTOR. INTERMEDIATE SPACERS MAY BE USED
TO MAINTAIN CONDUCTOR SPACING AND PROVIDE SUPPORT.
1981 EDITION
WHERE THERE ARE CURBS, THE MEASUREMENT FROM THE STREET SIDE OF THE CURB
TO THE SUPPORTING STRUCTURE, SUPPORT ARMS, AND EQUIPMENT ATTACHED THERETO
UP TO 15 FT. ABOVE THE ROAD SURFACE.
A. SHALL BE NOT LESS THAN 6 IN.
B. SHOULD BE NOT LESS THAN 2 FT. ON MATERIALS WHICH ARE PRIMARILY USED
FOR THROUGH TRAFFIC, USUALLY ON A CONTINUOUS ROUTE.
c. SHOULD BE NOT LESS THAN 1 FT. ON LOCAL STREETS AND ROADS WHICH ARE
PRIMARILY USED FOR ACCESS TO RESIDENCES, BUSINESSES, OR OTHER
ABUTTING PROPERTIES.
RECOMMENDATION: WHERE SUFFICIENT BORDER SPACE IS AVAILABLE WITHIN
THE STREET, ROAD, OR HIGHWAY RIGHT-OF-WAY, PLACEMENT OF SUPPORTING
STRUCTURES AS FAR AS IS PRACTICAL BEHIND THE CURBS IS RECOMMENDED.
LOCATION BEHIND SIDEWALKS IS DESIRABLE.
NESC Seminar/Misc.
RULE 231B
RULE 231C
1984 EDITION
WHERE THERE ARE CURBS, SUPPORTING STRUCTURES AND SUPPORT ARMS, OR EQUIPMENT ATTACHED THERETO, UP TO 15 FT. (4.6m) ABOVE THE ROAD SURFACE, SHALL BE LOCATED A SUFFICIENT DISTANCE FROM THE STREET SIDE OF THE CURBS TO AVOID CONTACT BY ORDINARY VEHICLES USING AND LOCATED ON THE TRAVELED WAY. IN NO CASE SHALL SUCH DISTANCE BE LESS THAN 6 IN. (150mm).
1981 EDITION
WHERE THERE ARE NO CURBS, SUPPORTING STRUCTURES SHOULD BE AT OR AS NEAR
AS IS PRACTICAL TO THE STREET, ROAD, OR HIGHWAY RIGHT-OF-WAY LINE.
1984 EDITION
WHERE THERE ARE NO CURBS, SUPPORTING STRUCTURES SHOULD BE LOCATED A
SUFFICIENT DISTANCE FROM THE ROADWAY TO AVOID CONTACT BY ORDINARY
VEHICLES USING AND LOCATED ON THE TRAVELED WAY.
1984 EDITION
EXCEPTION 4: AT INDUSTRIAL SIDINGS, A CLEARANCE OF NOT LESS THAN 7 FEET
(2.13m) SHALL BE PERMITTED, PROVIDED SUFFICIENT SPACE IS LEFT WHERE CARS CAN BE LOADED OR UNLOADED.
NESC Seminar/Miec,
TABLE 232-1 1984 EDITION
FOOTENOTE 8
THIS CLEARANCE MAY BE REDUCED TO THE FOLLOWING VALUES:
(A) 12 FT. FOR SUPPLY CONDUCTORS LIMITED TO 300 V TO GROUND
(B) 10 FT. FOR DRIP LOOPS OF SERVICE DROP CONDUCTORS LIMITED TO
0 VY TO GROUND MEETING RULES 0C2 OR 230C3 AND THE
PORTION OF THE ASSOCIATED SERVICE DROP SPAN LOCATED WITHIN
15 FT. OF THE SERVICE ENTRANCE TO BUILIDINGS.
TABLE 232-1 1984 EDITION
FOOTENOTE 22
FOR THE PURPOSE OF THIS RULE, TRUCKS ARE DEFINED AS ANY VEHICLE EXCEEDING
8 FT. IN HEIGHT. AREAS NOT SUBJECT TO TRUCK FI E
TRUCK TRAFFIC IS NOT NORMALLY ENCOUNTERED OR NOT REASONABLY ANTICIPATED.
TABLE 232-1 1984 EDITION
FOOTNOTE 24
THIS CLEARANCE MAY BE REDUCED TO 10 FT. FOR COMMUNICATION CONDUCTORS AND
CABLES, GUYS, MESSENGERS AND SUPPLY CABLES MEETING Cl.
NESC Seminar/Misc.
TABLE 232-1 1984 EDITION
RULE 232B2
d.
RULE 233A
FOOTNOTE 25
COMMUNICATION CABLES SUPPORTED ON A STEEL MESSENGER MAY HAVE A_ 60°F CLEARANCE OF 15 FEET WHERE SPAN LENGTHS DO NOT EXCEED 150 FEET AND POLES ARE BACK OF CURBS OR OTHER DETERRENTS TO VEHICULAR TRAFFIC.
1984 EDITION
E_ PHASE AND NEUTRAL CONDUCTORS OF A SUPPLY LINE SHOULD BE NOTE: THE PHASE _AND NEUTRAL CONDUCTORS OF _A SUPPLY _ LINE SHOULD BE CONSIDERED SEPARATELY WHEN DETERMINING THE SAG INCREASES OF EACH DUE TO TEMPERATURE RISE.
1984 EDITION
GENERAL
CROSSINGS SHOULD BE MADE ON A _ COMMON SUPPORTING STRUCTURE, WHERE PRACTICAL. IN OTHER CASES, THE CLEARANCE BETWEEN ANY TWO CROSSINGS OR ADJACENT WIRES, CONDUCTORS, OR CABLES CARRIED ON DIFFERENT SUPPORTING STRUCTURES SHALL NOT BE ANY LESS AT ANY LOCATION IN THE SPANS THAN THAT REQUIRED BY RULE 233. THE MINIMUM CLEARANCE SHALL BE AS ILLUSTRATED BY A CLEARANCE ENVELOPE DEVELOPED UNDER RULE 233A2 APPLIED AT THE POSITIONS ON OR WITHIN CONDUCTOR MOVEMENT he DEVELOPED UNDER RULE 233Al AT WHICH THE TWO WIRES, CONDUCTOR E HER. FOR PURPOSES OF THIS DET ERHTNATION, THE RELEVANT POSITIONS OF THE WIRES, CONDUCTORS, OR CABLES ON OR WITHIN THEIR RESPECTIVE CONDUCTOR MOVEME ENVELOPES ARE THOSE WHICH C. E OTH ARE SIMULTANEOUSLY SUBJECTED TO THE SAME AMBIENT AIR TEMPERATURE AND WIND LOADING CONDITIONS AND (2) EACH IS SUBJECTED INDIVIDUALLY TO THE FULL RANGE OF ITS ICING CONDITIONS AND APPLICABLE DESIGN ELECTRICAL LOADING.
NESC Seminar/Misc,
RULE 233B
1.
TABLE 233-1
TABLE 233-1
1984 EDITION
EXCEPTION: THE HORIZONTAL CLEARANCE BETWEEN ANCHOR GUYS OF DIFFERENT
SUPPORTING STRUCTURES MAY BE REDUCED TO 6 IN. (150mm) AND MAY BE REDUCED
TO 2 FT. (600mm) BETWEEN OTHER GUYS, SPAN WIRES AND NEUTRAL CONDUCTORS MEETING RULE 230E1.
1981 EDITION
FOOTNOTE 5
THIS CLEARANCE SHALL BE INCREASED TO 6 FT. WHERE THE SUPPLY WIRES CROSS OVER A COMMUNICATION LINE WITHIN 6 FT. HORIZONTALLY OF A COMMUNICATION
STRUCTURE.
1984 EDITION
FOOTNOTE 5
THIS CLEARANCE MAY BE REDUCED TO 4 FT. WHERE SUPPLY CONDUCTORS OF 750 V
TO 8.7 KV CROSS A COMMUNICATION LINE MORE THAN 6 FT. HORIZONTALLY FROM A
COMMUNICATION STRUCTURE.
NESC Seminar/Misc.
RULE 233C
Js
RULE 234C4
1984 EDITION
ALTERNATE CLEARANCES FOR VOLTAGES EXCEEDING 98 KILOVOLTS ALTERNATING
CURRENT TO GROUND OR 139 KILOVOLTS DIRECT CURRENT TO GROUND.
THE CLEARANCES SPECIFIED IN RULES 233C1 AND 233C2 MAY BE REDUCED WHERE THE HIGHER VOLTAGE CIRCUIT HAS A KNOWN SWITCHING SURGE FACTOR. FOR THESE COMPUTATIONS, COMMUNICATION CONDUCTORS AND CABLES, GUYS, MESSENGERS, NEUTRAL CONDUCTORS MEETING RULE 230E1, AND SUPPLY CABLES MEETNG RULE 230C1 SHALL BE CONSIDERED AT ZERO VOLTAGE. THE CLEARANCES SHALL NOT BE LESS THAN THE VALUES COMPUTED BY ADDING THE REFERENCE HEIGHTS TO THE ELECTRICAL COMPONENT OF CLEARANCE.
1984 EDITION
SERVICE-DROP CONDUCTORS SHALL NOT BE READILY ACCESSIBLE AND WHEN NOT IN
EXCESS OF 600 VOLTS THEY SHALL HAVE A CLEARANCE OF NOT LESS THAN THE
FOLLOWING:
(1) 8 FT. (2.45m) FROM THE HIGHEST POINT OF ROOFS OR BALCONIES OVER WHICH THEY PASS.
EXCEPTION 1: WHERE THE VOLTAGE BETWEEN CONDUCTORS DOES NOT EXCEED 300 VOLTS AND THE ROOF OR BALCONY IS NOT READILY ACCESSIBLE, THE CLEARANCE MAY BE NOT LESS THAN 3 FT. (900mm). A ROOF OR BALCONY IS CONSIDERED READILY ACCESSIBLE IF THE MEANS OF ACCESS IS THROUGH A DOORWAY, RAMP, STAIRWAY, OR PERMANENTLY MOUNTED LADDER.
EXCEPTION 2: SERVICE-DROP CONDUCTORS OF 300 VOLTS OR LESS WHICH DO NOT PASS OVER OTHER THAN A MAXIMUM OF 4 FT. (1.20m) OF THE OVERHANG PORTION OF THE ROOF FOR THE PURPOSE OF TERMINATING AT A (THROUGH- THE-ROOF) SERVICE RACEWAY OR APPROVED SUPPORT, MAY BE MAINTAINED AT A MINIMUM OF 18 IN. (450mm) FROM ANY PORTION OF THE ROOF OVER WHICH THEY PASS.
NESC Seminer/Mien,
RULE 234C4
RULE 234E.
1.
RULE 235B
3.
1984 EDITION
(2) 3 FT. (900mm) IN ANY DIRECTION FROM WINDOWS, DOORS, PORCHES, FIRE
ESCAPES, OR SIMILAR LOCATIONS.
EXCEPTION 1: THIS DOES NOT APPLY TO SERVICE-DROP CONDUCTORS MEETING
RULE 230C3 ABOVE THE TOP LEVEL OF A WINDOW,
EXCEPTION 2: THIS DOES NOT APPLY TO WINDOWS THAT ARE NOT DESIGNED
TO OPEN.
1984 EDITION
EXCEPTION 2: THIS RULE DOES NOT APPLY TO: COMMUNICATION CONDUCTORS AND
CABLES, GUYS AND MESSENGERS, SUPPLY CABLES MEETING RULE C SUPPLY
CABLES OF 0 TO 750 V MEETING RULES 230C2 OR 230C3; WHEN THESE FACILITIES
ARE TEN FEET OR MORE HORIZONTALLY FROM THE EDGE OF THE POOL, DIVING PLAT—
FORM, OR DIVING TOWER.
1984 EDITION
ALTERNATE CLEARANCES FOR DIFFERENT CIRCUITS WHERE ONE OR BOTH CIRCUITS
EXCEED 98 KILOVOLTS, ALTERNATING CURRENT, TO GROUND OR 139 KILOVOLTS
DIRECT CURRENT TO GROUND.
THE CLEARANCES SPECIFIED IN RULES 235Bl and 235B2 MAY BE REDUCED FOR
CIRCUITS WITH KNOWN SWITCHING SURGE FACTORS BUT SHALL NOT BE LESS THAN
THE CLEARANCES DERIVED FROM THE FOLLOWING COMPUTATIONS. FOR THESE
COMPUTATIONS, COMMUNICATION CONDUCTORS AND CABLES, GUYS, MESSENGERS,
NEUTRAL CONDUCTORS MEETING RULE 230E1, AND SUPPLY CABLES MEETING RULE
230C1 SHALL BE CONSIDERED A LINE CONDUCTOR AT ZERO VOLTAGE.
NESC Seminar/Misc.
RULE 235C2 1984 EDITION
B. CONDUTORS OF DIFFERENT SAGS ON SAME SUPPORT
(1) LINE CONDUCTORS, SUPPORTED AT DIFFERENT LEVELS ON THE SAME STRUCTURE
SHALL HAVE VERTICAL CLEARANCES AT THE SUPPORTING STRUCTURES SO
ADJUSTED THAT THE MINIMUM CLEARANCE AT ANY POINT IN THE SPAN SHALL
BE NOT LESS THAN ANY OF THE FOLLOWING WITH THE UPPER CONDUCTOR AT
ITS FINAL UNLOADED SAG AT THE MAXIMUM TEMPERATURE FOR WHICH THE
CONDUCTOR IS DESIGNED TO OPERATE AND THE LOWER CONDUCTOR AT ITS
FINAL UNLOADED SAG, UNDER THE SAME AMBIENT CONDITIONS AND WITHOUT
ELECTRICAL LOADING.
(a) FOR VOLTAGES LESS THAN 50 KILOVOLTS BETWEEN CONDUCTORS, 75
PERCENT OF THAT REQUIRED AT THE SUPPORTS BY TABLE 235-5.
(B) FOR VOLTAGES MORE THAN 50 KILOVOLTS BETWEEN CONDUCTORS, THE VALUE SPECIFIED IN RULE 235C2b(1)(a) INCREASED IN ACCORDANCE WITH RULE 235C2a.
TABLE 235-6 1984 EDITION
FOOTNOTE 1
FOR GUY WIRES, IF PRACTICAL. FOR CLEARANCES BETWEEN SPAN WIRES AND COM-
MUNICATION CONDUCTORS, SEE RULE 238C.
ON JOINTLY USED STRUCTURES, GUYS WHICH PASS WITHIN 12 IN. OF SUPPLY
CONDUCTORS, AND ALSO PASS WITHIN 12 IN. OF COMMUNICATION CABLES, SHALL BE
PROTECTED WITH A SUITABLE INSULATING COVERING WHERE THE GUY PASSES THE
SUPPLY CONDUCTORS, UNLESS THE GUY IS EFFECTIVELY GROUNDED OR INSULATED
WITH A STRAIN INSULATOR AT A POINT BELOW THE LOWEST SUPPLY CONDUCTOR AND
ABOVE THE HIGHEST COMMUNICATION CABLE.
THE MINIMUM CLEARANCE FROM AN INSULATED OR EFFECTIVELY GROUNDED GUY, TO A
COMMUNICATION CABLE, MAY BE REDUCED TO 3 INCHES WHEN ABRASION PROTECTION IS PROVIDED ON THE GUY OR COMMUNICATION CABLE.
NESC Seminar/Mi ec,
TABLE 235-6 1984 EDITION
RULE 238
RULE 238
RULE 238D
FOOTNOTE 11
THESE CLEARANCES MAY BE REDUCED BY NOT MORE THAN 25 PERCENT TO A GUY
INSULATOR, PROVIDED THAT FULL CLEARANCE IS MAINTAINED TO ITS METALLIC END
FITTINGS 5 AND THE GUY WIRES. THE CLEARANCE TO AN INSULATED SECTION OF A
GUY BETWEEN TWO INSULATORS MAY BE REDUCED BY NOT MORE THAN 25 PERCENT
PROVIDED THAT FULL CLEARANCE IS MAINTAINED TO THE UNINSULATED PORTION OF
THE GUY.
1981 EDITION
VERTICAL CLEARANCE BETWEEN LINE WIRES, CONDUCTORS, OR CABLES AND
NONCURRENT—CARRYING METAL PARTS OF EQUIPMENT LOCATED AT DIFFERENT LEVELS
ON THE SAME STRUCTURE.
1984 EDITION
VERTICAL CLEARANCE BETWEEN CERTAIN COMMUNICATION AND SUPPLY FACILITIES
LOCATED ON THE SAME STRUCTURE.
1984 EDITION
EXCEPTION: | THE ABOVE CLEARANCE MAY BE REDUCED TO 3 IN. (75mm) IF THE
LOOP IS COVERED BY A SUITABLE NON-METALLIC COVERING WHICH EXTENDS AT LEAST 2 IN. (50mm) BEYOND THE LOOP.
NESC Seminar/Misc.
RULE 239D2a 1981 EDITION
(3) GROUNDING CONDUCTORS MAY BE RUN ON THE POLE SURFACE WITHOUT MOLDING.
RULE 239D2a 1984 EDITION
(3)
RULE 239F
7.
RULE 241C
SUPPLY GROUNDING CONDUCTORS MAY BE RUN ON THE POLE SURFACE WITHOUT
MOLDING, EXCEPT AS REQUIRED BY RULE 239C FOR MECHANICAL PROTECTION NEAR THE GROUND.
1984 EDITION
MULTIPLE CONDUCTOR CABLES
MULTIPLE CONDUCTOR CABLES OPERATING AT VOLTAGES NOT EXCEEDING 600 V BETWEEN CONDUCTORS MAY BE ATTACHED DIRECTLY TO THE SURFACE OF THE LINE STRUCTURE IF PROTECTED BY NON-METALLIC COVERING. EACH CONDUCTOR SHALL BE LNSULATED FOR A POTENTIAL OF AT LEAST 600 V. WHERE USED AS AERIAL SERVICES, THE POINT WHERE SUCH CABLES LEA E SHALL BE AT
COMMUNICATIONS _ATTACHMENT. ALL SPLICES AND CONNECTIONS IN THE “CABLE
SHALL BE INSULATED.
1984 EDITION
AT CROSSINGS
WIRES, CONDUCTORS OR OTHER CABLES OF ONE LINE ARE CONSIDERED TO BE AT CROSSINGS WHEN THEY CROSS } OVER _ ANOTHER LINE, WHETHER OR NOT ON A COMMON SUPPORTING STRUCTURE, OR WHEN THEY CROSS OVER OR OVERHANG A RATLROAD TRACK OR THE TRAVELED WAY OF A LIMITED ACCESS HIGHWAY. JOINT—-USE OR COLINEAR CONSTRUCTION IN ITSELF IS NOT CONSIDERED TO BE AT CROSSINGS.
NESC Seminar/Micc,
RULE 242F
RULE 282B
SECTION 31
RULE 310
1984 EDITION
SURGE PROTECTION WIRES
SURGE PROTECTION WIRES SHALL BE OF THE SAME GRADE OF CONSTRUCTION AS THE
SUPPLY CONDUCTORS WITH WHICH THEY ARE ASSOCIATED.
1984 EDITION
STRENGTH
THE STRENGTH OF THE GUY OR BRACE SHALL MEET THE REQUIREMENTS OF SECTION 26 FOR THE APPLICABLE GRADE OF CONSTRUCTION.
FOR GUY WIRES CONFORMING TO ANSI/ASTM STANDARDS, THE MINIMUM BREAKING
STRENGTH VALUE THEREIN DEFINED SHALL BE THE RATED BREAKING STRENGTH
REQUIRED IN THIS CODE.
1984 EDITION
REFERENCED SECTIONS
THE INTRODUCTION (SECTION 1), DEFINITIONS (SECTION 2 LIST OF REFERENCED
DOCUMENTS (SECTION AND GROUNDING METHODS (SECTION 9) OF THIS CODE
SHALL APPLY TO THE REQUIREMENTS OF PART 3.
NESC Seminar/Misc.
RULE 313A
RULE 316
1984 EDITION
INSPECTION
ACCESSIBLE LINE AND EQUIPMENT SHALL BE INSPECTED -FROM—FEME—TO-—TIME BY THE
RESPONSIBLE PARTY AT SUCH INTERVALS AS EXPERIENCE HAS SHOWN TO BE
NECESSARY.
1984 EDITION
INDUCED VOLTAGE
RULES COVERING SUPPLY LINE INFLUENCE AND COMMUNICATION LINE
SUSCEPTIVENESS HAVE NOT BEEN DETAILED IN THIS CODE. COOPERATIVE
ROCEDURES ARE RECOMMENDED TO MINIMIZE STEADY STATE ILTAGES IT CED FROM
PROXIMATE FACILITIES. THEREFORE, REASONAB:
GIVEN TO OWNERS OR OPERATORS OF OTHER KNOWN PROXIMATE FACILITIES WHICH
MAY BE ADVERSELY AFFECTED BY NEW CONSTRUCTION OR CHANGES IN EXISTING
FACILITIES.
NES® Seminar/Mier,
RULE 381G
RULE 402
RULE 410C
1.
1984 EDITION
WHERE PAD-MOUNTED EQUIPMENT IS NOT WITHIN A FENCED OR OTHERWISE PROTECTED
AREA, ACCESS TO EXPOSED LIVE PARTS IN EXCESS OF 600 V SHALL REQUIRE TWO
SEPARATE CONSCIOUS ACTS. ONE SHALL BE THE OPENING OF A DOOR OR BARRIER
WHICH IS LOCKED OR OTHERWISE SECURED AGAINST UNAUTHORIZED ENTRY. THE
OTHER SHALL BE EITHER THE OPENING OR THE REMOVAL OF A SECOND SECURED DOOR
OR BARRIER.
RECOMMENDATION: A PROMINENT WARNING SIGN SHOULD BE PLACED IN THE SECOND
DOOR OR B. I B N IRST IS OPENED OR REMOVED.
1984 EDITION
REFERENCED SECTIONS
THE INTRODUCTION (SECTION 1), DEFINITIONS (SECTION 2), LIST OF REFERENCED
DOCUMENTS (SECTION 3) AND GROUNDING METHODS CECT MED) OF THIS on SHALL APPLY TO THE REQUIREMENTS OF PART 4,
THE AMERICAN NATIONAL STANDARDS LISTED IN SECTION 3 SHALL BE USED WITH
PART 4 WHERE APPLICABLE.
NOTE: AFTER ANSI C2.4-1973 WAS ORIGINALLY APPROVED 30 JUNE 1972, OSHA (OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION) ISSUED 29CFR1926 SUBPART V APPLYING TO EMPLOYEE SAFETY IN CONSTRUCTION. THE 1984 EDITION REVISIONS DID NOT ADDRESS THE DIFFERENCES. FOOTNOTES HAVE BEEN PROVIDED IN THE TEXT WHERE OS REQUIREMENTS CONFLI WITH REQUIREMENTS .
1984 EDITION
A DESIGNATED PERSON SHALL BE IN CHARGE OF THE OPERATION OF THE EQUIPMENT
AND LINES AND SHALL BE RESPONSIBLE FOR THEIR SAFE OPERATION.
NESC Seminar/Misc.
RULE 420B
Ds
RULE 420C
3.
RULE 4200
1984 EDITION
SWITCHGEAR SHALL BE DE-ENERGIZED PRIOR TO PERFORMING WORK INVOLVING
REMOVAL OF PROTECTIVE BARRIERS UNLESS OTHER SUITABLE MEANS ARE PROVIDED
FOR EMPLOYEE PROTECTION. THE PERSONNEL SAFETY FEATURES IN SWITCHGEAR SHALL BE REPLACED AFTER WORK IS COMPLETED.
1984 EDITION
IF AN EMPLOYEE IS IN DOUBT AS TO THE SAFE PERFORMANCE OF ANY ASSIGNED
WORK, THE EMPLOYEE SHALL REQUEST INSTRUCTIONS FROM THE EMPLOYEE'S
SUPERVISOR OR OTHER QUALIFIED PERSON.
1984 EDITION
FUSES
WHEN FUSES MUST BE INSTALLED OR REMOVED WITH ONE OR BOTH TERMINALS
ENERGIZED ABOVE 1 KV, SPECIAL TOOLS INSULATED FOR THE VOLTAGE OR
ADEQUATELY RATED GLOVES SHALL BE USED. INSULATING TOOLS OR GLOVES SHOULD
BE USED FOR VOLTAGES BETWEEN 300 AND 1000. WHEN INSTALLING EXPULSION
TYPE FUSES, EMPLOYEES SHALL WEAR PERSONAL EYE PROTECTION AND TAKE
PRECAUTIONS TO STAND CLEAR OF THE EXHAUST PATH OF THE FUSE BARREL.
NESC Seminar/Mier,
RULE 420Q
RULE 421A
1984 EDITION
GAS-INSULATED EQUIPMENT
EMPLOYEE WORKING ON GAS-INSULATED CABLE SYSTEMS OR CIRCUIT BREAKERS SHALL
BE INSTRUCTED CONCERNING THE SPECIAL PRECAUTIONS REQUIRED FOR POSSIBLE
PRESENCE OF BY-PRODUCTS OF SF¢.
NOTE: BY-PRODUCTS RESULTING FROM ARCING IN SULPHUR-HEXAFLUORIDE (SF¢)
GAS-INSULATED SYSTEMS ARE GENERALLY TOXIC AND IRRITANT. GASEOUS _BY-
PRODUCTS CAN BE REMOVED FOR MAINTENANCE ON THE COMPARTMENTS BY PURGING
WITH AIR OR DRY NITROGEN. THE SOLID RESIDUE THAT MUST BE REMOVED IS
MOSTLY METALLIC. THIS FINE POWDER ABSORBS MOISTURE AND PRODUCES GASEOUS
FLUORIDES OF SULPHUR AND HYDROFLUORIC ACID, WHICH ARE TOXIC AND
CORROSIVE.
1984 EDITION
DUTIES OF A DESIGNATED PERSON
A_ DESIGNATED PERSON SHALL:
1. KEEP INFORMED OF OPERATING CONDITIONS AFFECTING THE SAFE AND
RELIABLE OPERATION OF THE SYSTEM.
2. MAINTAIN A SUITABLE RECORD SHOWING OPERATING CHANGES IN SUCH
CONDITIONS.
NESC Seminar/Misc.
RULE 421B
RULE 4211
RULE 4211
1984 EDITION
DUTIES OF A FIRST LINE SUPERVISOR
A FIRST LINE SUPERVISOR SHALL:
1. ADOPT SUCH PRECAUTIONS AS ARE WITHIN THE FIRST LINE
SUPERVISOR'S POWER TO PREVENT ACCIDENTS AND TO SEE THAT THE
SAFETY RULES AND OPERATING PROCEDURES ARE OBSERVED BY THE
EMPLOYEES UNDER THE DIRECTION OF THE FIRST LINE SUPERVISOR.
Ze MAKE ALL THE NECESSARY RECORDS AND REPORT TO THE SYSTEM
OPERATOR WHEN REQUIRED.
3. AS FAR AS _ POSSIBLE, PREVENT UNAUTHORIZED PERSONS FROM
APPROACHING PLACES WHERE WORK IS BEING DONE.
4. PROHIBIT THE USE OF ANY TOOLS OR DEVICES UNSUITED TO THE WORK AT HAND OR WHICH HAVE NOT BEEN TESTED OR INSPECTED AS REQUIRED
BY THESE RULES.
1981 EDITION
PROTECTING EMPLOYEES BY SWITCHES AND DISCONNECTORS
WHEN EQUIPMENT OR LINES ARE TO BE DISCONNECTED FROM ANY SOURCE OF ELECTRIC ENERGY FOR THE PROTECTION OF EMPLOYEES, THE OPERATOR SHALL FIRST OPEN THE SWITCHES OR CIRCUIT BREAKERS DESIGNATED FOR OPERATION UNDER THE LOAD INVOLVED.
1984 EDTION
PROTECTING EMPLOYEES BY SWITCHES AND DISCONNECTORS
WHEN EQUIPMENT OR LINES ARE TO BE DISCONNECTED FROM ANY SOURCE OF ELECTRIC ENERGY FOR THE PROTECTION OF EMPLOYEES, THE SWITCHES OR CIRCUIT BREAKERS DESIGNATED FOR OPERATION UNDER THE LOAD INVOLVED SHALL BE OPENED FIRST.
NESC Seminar/Misc.
RULE 423A
3.
RULE 423C
1984 EDITION
RECORDS SHALL BE KEPT ON ALL CONTRACTUAL UTILITY INTERACTIVE SYSTEMS ON
ANY ELECTRIC SUPPLY LINES. WHEN THESE LINES ARE DE-ENERGIZED PER RULE
423C, THE UTILITY INTERACTIVE SYSTEM SHALL BE VISIBLY DISCONNECTED FROM
THE LINES.
1984 EDITION
OPENING DISCONNECTORS AND TAGGING
THE DESIGNATED PERSON SHALL DIRECT THE OPENING OF ALL SWITCHES AND DISCONNECTORS THROUGH WHICH ELECTRIC ENERGY MAY BE SUPLIED TO THE
PARTICULAR SECTION OF EQUIPMENT AND LINES TO BE DE-ENERGIZED, AND SHALL
DIRECT THAT SUCH SWITCHES AND DISCONNECTORS BE RENDERED INOPERABLE AND
TAGGED PLAINLY INDICATING THAT PERSONS ARE AT WORK.
IF SWITCHES THAT ARE CONTROLLED AUTOMATICALLY, OR REMOTELY, OR BOTH CAN
BE RENDERED INOPERABLE THEY SHALL BE TAGGED AT THE SWITCH LOCATED. IF IT
IS IMPRACTICAL TO RENDER SUCH SWITCHES AND DISCONNECTORS INOPERABLE THEN
THESE REMOTELY CONTROLLED SWITCHES SHALL ALSO BE TAGGED AT ALL POINTS OF
CONTROL.
A RECORD SHALL BE MADE WHEN PLACING THE TAG GIVING THE TIME OF DISCON-
NECTION, THE NAME OF THE MAKING THE DISCONNECTION, THE NAME OF THE
EMPLOYEE WHO REQUESTED THE DISCONNECTION, AND THE NAME, OR TITLE, OR
BOTH, OF THE DESIGNATED PERSON.
NESC Seminar/Misc.
RULE 423D
RULE 423E
1984 EDITION
EMPLOYEE'S PROTECITVE GROUNDS
WHEN ALL THE SWITCHES AND DISCONNECTORS DESIGNATED HAVE BEEN OPENED,
RENDERED INOPERABLE, WHERE PRACTICAL, AND TAGGED IN ACCORDANCE WITH RULE
423C, AND THE EMPLOYEE HAS BEEN GIVEN PERSMISSION TO WORK BY THE
DESIGNATED PERSON, THE EMPLOYEE IN CHARGE SHOULD IMMEDIATELY PROCEED TO
MAKE HIS OWN PROTECTIVE GROUNDS OR VERIFY THAT ADEQUATE GROUNDS HAVE BEEN
APPLIED (SEE RULE 424) ON THE DISCONNECTED LINES OR EQUIPMENT.
GROUNDS SHALL BE PLACED EACH SIDE OF THE WORK LOCATION AND AS CLOSE AS
PRACTICAL TO THE WORK LOCATION, OR A SINGLE GROUND POINT SHALL BE PLACED
AT THE WORK LOCATION. IF WORK IS TO BE PERFORMED AT MORE THAN ONE
LOCATION ON A LINE SECTION, THE LINE SECTION SHALL BE GROUNDED AND . SHORT
CIRCUITED AT ONE LOCATION IN THE LINE SECTION AND THE CONDUCTOR TO BE
WORKED ON SHALL BE GROUNDED AT EACH WORK LOCATION.
THE MINIMUM DISTANCE IN TABLE 422-1,2,3 OR 4 AS APPLICABLE SHALL BE
MAINTAINED FROM UNGROUNDED CONDUCTORS AT THE WORK LOCATION. WHERE THE
MAKING OF A GROUND IS IMPRACTICAL, OR THE CONDITIONS RESULTING THEREFROM
HAZ. ORKING H IPME) WITHO
GROUNDING, THE GROUND MAY BE OMITTED BY SPECIAL PERSMISSION OF THE
DESIGNATED PERSON.
1984 EDITION
PROCEEDING WITH WORK
AFTER THE EQUIPMENT OR LINES HAVE BEEN DE-ENERGIZED AND GROUNDED, THE
EMPLOYEE IN CHARGE AND THOSE UNDER THE DIRECTION OF THE EMPLOYEE IN
CHARGE MAY PROCEED WITH WORK ON THE DE-ENERGIZED PARTS. EQUIPMENT MAY BE
RE-ENERGIZED FOR TESTING PURPOSED ONLY UNDER THE SUPERVISION OF THE
EMPLOYEE IN CHARGE AND SUBJECT TO AUTHORIZATION BY THE DESIGNATED PERSON.
NESC Seminar/Misc.
RULE 423E
2.
RULE 423F
RULE 423G
1984 EDITION
EACH ADDITIONAL EMPLOYEE IN CHARGE DESIRING THE SAME EQUIPMENT OR LINES
JO BE DE-ENERGIZED FOR THE PROTECTION OF THAT PERSON, OR THE PERSONS UNDER DIRECTION, SHALL FOLLOW THESE PROCEDURES TO SECURE SIMILAR
PROTECTION.
1984 EDITION
REPORTING CLEAR —— TRANSFERRING RESPONSIBILITY
THE EMPLOYEE IN CHARGE, UPON COMPLETION OF THE WORK AND AFTER ASSURING
SHALL REMOVE PROTECTIVE GROUNDS AND SHALL REPORT TO THE DESIGNATED PERSON
THAT ALL TAGS PROTECTING THAT PERSON MAY BE REMOVED.
THE EMPLOYEE IN CHARGE WHO RECEIVED THAT PERSMISSION TO WORK MAY, IF
SPECIFICALLY PERMITTED BY THE DESIGNATED PERSON, TRANSFER THE PERSMISSION |
TO WORK AND THE REPONSIBILITY FOR PERSONS BY PERSONALLY INFORMING THE
AFFECTED PERSONS OF THE TRANSFER.
1984 EDITION
REMOVAL OF TAGS
THE DESIGNATED PERSON SHALL THEN DIRECT THE REMOVAL OF TAGS AND THE
REMOVAL SHALL BE REPORTED BACK TO THE DESIGNATED PERSON BY THE PERSONS
REMOVING THEM. UPON THE REMOVAL OF ANY TAG, THERE SHALL BE ADDED TO THE
RECORD CONTAINING THE NAME OF THE DESIGNATED PERS OR TITLE OTH ,
AND THE PERSON WHO REQUESTED THE TAG, THE NAME OF THE PERSON REQUESTING
REMOVAL, THE TIME OF REMOVAL, AND THE NAME OF THE PERSON REMOVING THE
TAG.
THE NAME OF THE PERSON REQUESTING REMOVAL SHALL BE THE SAME AS THE NAME
OF THE PERSON REQUESTING PLACEMENT, UNLESS RESPONSIBILITY HAS BEEN
FERRED ACCORDING TO RULE 423F.
NESC Seminar/Misc.
RULE 423H 1984 EDITION
RESTORING SERVICE
ONLY AFTER ALL PROTECTIVE GROUNDS HAVE BEEN REMOVED FROM THE CIRCUIT OR EQUIPMENT AND AFTER ALL PROTECTIVE TAGS HAVE BEEN REMOVED IN ACCORDANCE WITH RULE 423G AT A SPECIFIC LOCATION, MAY THE DESIGNATED PERSON DIRECT THE CLOSING OF DISCONNECTORS AND SWITCHES AT THAT LOCATION.
RULE 433D 1984 EDITION
FLAMES
i. EMPLOYEES SHALL NOT SMOKE IN MANHOLES OR VAULTS UNTIL THE ATMOSPHERE AND AREA HAVE BEEN INSPECTE T
OR LIQUIDS AND ADEQUATE VENTILATION IS PROVIDED.
2. WHERE OPEN FLAMES MUST BE USED IN MANHOLES OR VAULTS, EXTRA PRECAUTIONS SHALL BE TAKEN TO ENSURE ADEQUATE VENTILATION.
3. BEFORE USING OPEN FLAMES IN AN EXCAVATION IN AREAS WHERE COMBUSTIBLE GASES OR LIQUIDS MAY BE PRESENT, SUCH AS NEAR GASOLINE SERVICE STATIONS, THE ATMOSPHERE OF THE EXCAVATION SHALL BE TESTED AND FOUND SAFE OR CLEARED OF THE COMBUSTIBLE GASES OR LIQUIDS.
NESC Seminar/Misc.