Major Changes in the 2017National Electrical Safety Code® (NESC®)

forPart 1-Electric Supply Stations

October 18, 2016 San Antonio, Texas

Marne and Associates, Inc.Experts in Electrical Code619 S.W. Higgins, Suite C

Missoula, MT 59803(406) 544-8997

www.marneassociates.comDavid J. Marne, P.E.

Overview¾ 2017 National Electrical Safety Code (NESC)

– Over 700 proposed changes were submitted to the NESC subcommittees.

– The accepted changes affect approximately 215 of the 354 pages in the NESC.

– Changes range from new rules and requirements to minor modifications of existing rules. (Not every change will be discussed.)

– NESC 2017 Edition was published August 1, 2016.– McGraw-Hill’s 2017 NESC Handbook was published October 1,

2016.– The Figures and Photos in this presentation are from McGraw-

Hill’s NESC 2017 Handbook and are used with permission of Marne and Associates, Inc. and the McGraw-Hill Companies, Inc. © 2017. Do not duplicate.

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2017 National Electrical Safety Code (NESC) Changes

¾ No Changes (General Overview)

¾ Level 1 (Minor Change)

¾ Level 2 (Moderate Change)

¾ Level 3 (Major Change)

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2017 National Electrical Safety Code (NESC) Changes

¾ NESC Change Bars

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Part 1- Electric Supply Stations

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Part 1- Electric Supply StationsQ: What separates Part 1-Electric Supply Stations from Part 2-Overhead Lines and Part 3-Underground Lines???

A: The Fence!!!

Safety sign locations on an electric supply station with and without a roof

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Change: RULE 110A.Modified rule wording for safety sign requirements on fenced substations and added rule wording for safety sign requirements on a substation with a roof.

Safe sign locations on an electric supply station with and without a roof

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Change: RULE 110A.Modified rule wording for safety sign requirements on fenced substations and added rule wording for safety sign requirements on a substation with a roof.

Barrier height requirements

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Change: RULE 110A.Minor edits to the formatting and wording.

Remember! Dimensions are “Not Less Than” values and must be maintained.

Neighboring fence requirements

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Change: RULE 110A.New rule wording addressing neighboring fences adjacent to substation fences.

Neighboring fence requirements

¾ Photo submitted with NESC CP 4572 by Allen Clapp

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Example of how to apply the safety clearance zone to a chain-link fence per NESC Table 110-1 and NESC Fig. 110-1

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substation fence (safety clearance zone). Altitude of 3300’ or less.

¾ Example: 12.47/7.2 kV, 3∅, 4W live part clearance from a chain-link substation fence (safety clearance zone). Altitude of 3300’ or less.

Change: RULE 110A2a and Table 110-1. Added a requirement to apply appropriate atmospheric correction factors to the clearance values for altitudes above 3300 feet.

Example of how to apply the safety clearance zone to a chain-link fence per NESC Table 110-1 and NESC Fig. 110-1

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Example of how to apply the safety clearance zone to an impenetrable fence per NESC Table 110-1 and NESC Fig. 110-2

¾ Example:12.47/7.2 kV, 3∅, 4W live part clearance from an impenetrable fence (safety clearance zone). Altitude of 3300’ or less.

Change: RULE 110A2b.New rule wording addressing both penetrable and impenetrable portions of a fence.

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Fire-extinguishing equipment

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Change: Rule 114 was deleted.

Example of how to apply vertical clearances per NESC Table 124-1, NESC Fig. 124-1 and Rule 124A3

¾ Example:34.5/19.9 kV, 3∅, 4W primary 12.47/7.2 kV, 3∅, 4W, secondary Altitude of 3300’ or lessVertical clearance:35 kV between phases for primary.15 kV (110 kV BIL) between phases for secondary.Vertical clearance per NESC Table 124-1, Column 2

Change: RULE 124A1.Added a requirement to apply appropriateatmospheric correction factors to the clearance values for altitudes above 3300’.

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Example of how to apply vertical clearances per NESC Table 124-1, NESC Fig. 124-1, and Rule 124A3

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