PROPOSED CHANGES TO THE 2007 NATIONAL ELECTRICAL SAFETY

PROPOSED CHANGES TO THE 2007 NATIONAL ELECTRICAL SAFETY CODE

Time Schedule for 2007 Edition of NESC • July 17, 2003 Final date for receipt of proposals • Oct. 5 -24, 2003 NESC Subcommittees meet • Sept. 1, 2004 NESC Preprints published • May 1, 2005 Final date for receipt of public comments

Time Schedule for 2007 Edition of NESC • Oct. 2 -20, 2005 NESC Subcommittees reconsider recommendations • Jan. 15, 2006 Proposed revisions submitted to NESC Committee for ballot • May 15, 2006 NESC Committee submits approved revisions to ANSI • Aug. 1, 2006 2007 NESC published

CP 2528 - Section 2, Definitions • Relocates and revises the definition of “readily climbable supporting structure. ” • Combines “readily climbable” and “not readily climbable” under one definition. • Adds the notes that clarify what structures are considered not “readily climbable” to the code.

CP 2715 - Rule 94 B 7, Directly Embedded Metal Poles Allows directly embedded metal poles to be an acceptable grounding electrode if: • backfill is native backfill, concrete or conductive grout, • embedment is > 5’, • metal thickness is > ¼”, and • any protective coating is conductive.

CP 2508 - Rule 230, Uniform Clearance Calculations • Moves current Rule 250 B, Figure 250 -1 and Table 250 -1 to new Rule 230. • Retains the ice loading districts for determining clearances. • Changes “loading districts” to “loading zones. ” • Wind loading values revert to 4 th edition values. • Appendix B

CP 2508 - Rule 230, Uniform Clearance Calculations Wind loading values revert to 4 th edition values. • Wind values are 8 psf for Heavy and Medium; 10 psf for Light. • The “adder constants” (0. 3, 0. 2 & 0. 05) of Table 251 -1 were deleted. • This will produce approximately the same sags as the lesser wind pressure in the 2002 edition with the adder constant.

CP 2630 - Rule 232 B 3, Clearance to Support Arms, Switch Handles and Equipment Cases • Adds switch handles to the rule. • Requires a clearance of 15’ above areas accessible to truck traffic and 11’ under spaces and ways accessible to pedestrians if effectively grounded. • Does not address switch handles not grounded. • Excepts switch handles that “do not unduly obstruct a walkway. ”

CP 2826 - Rule 242, Grades of Construction for Conductors • Requires conductors crossing navigable waterways requiring crossing permits to be designed to Grade B construction. • Proposed because of downed overhead conductors hampering rescue craft during storm recovery efforts.

CP 2737 - Revision of Sections 25, 26 & 27 Proposes incorporating the Reliability Based Method for determining structure loading. • Consistent with ANSI/ASCE 7. • New combined ice and wind loading map. • Map based on 50 year ice and wind events. • Provides a new formula for extreme wind. • Eliminates the 60’ exclusion from extreme wind loading.

EXTREME WIND LOADING FORMULA Load in pounds = 0. 00256 (V 2) (k. Z) (Grf) ( I ) (Fg) (Cd) (A 2) • 0. 00256 = Ambient air density value • V 2 = Basic wind speed in miles per hour (squared) • Kz = Velocity pressure exposure coefficient. This value is defined in Tables 250 -1 & 250 -2 for open terrain and Tables 250 -3 & 250 -4 for sheltered terrain. • Grf = Gust response factor defined in tables 250 -1, 25 -0 -2, 250 -3 & 250 -4. • I = Importance factor, 1. 0 for utility structures and their supporting facilities • Fg = Factor for Grade of Construction (0. 87 for C, 1. 0 for B). • Cd = Shape factor from Rule 252 B 2 (Rules N 251 A & 251 B). • A 2 = Projected wind area squared in square feet

CP 2766 - Rule 250 C, EXTREME WIND Limits extreme loading on structures < 60’. • Limits 0. 00256 V 2 k. ZGRF to 15 psf for Grade C. • Limits 0. 00256 V 2 k. ZGRF to 30 psf for Grade B.

CP 2658 - Rule 250 D, Construction and Maintenance Loads Where maintenance & construction loads exceed the wind and ice load: • All conductor support points shall resist the bare conductor vertical loads expected to occur at sagging tensions times SF = 2. • All structural members supporting linemen shall be able to support 240# vertical load in addition to the max loads during maintenance. • When pulling thru stringing blocks, the pulling tension must be carefully controlled. If not, the pulling tension shall be applied to the block attachment point times SF=1. 5.

CP 2569 - Table 253 -1, Rule 261 A 3, Table 261 -1 A, Fiber-Reinforced Polymer Structures Addresses the strength requirements and the strength factors for fiberglass poles and crossarms.

CP 2622 - Rule 351 C, Location & Routing, Other Conditions • In response to IR 524. • Addresses the location of DB UG cable under an above ground pool. • Recommends that DB UG cable should not be installed directly under buildings or other structures unless the structure is suitably supported to limit transfer of a detrimental load onto the cable.

CP 2815 - Rule 410, General Requirements for Employers • Requires that by 2009, an arc assessment be performed for employees that work on or near energized parts. • If exposure > 2 cal/cm 2, FR clothing shall be worn. • For V < 1000 V, FR clothing with a min resistance of 4 cal/cm 2 shall be required. • For V > 1000 V, use Tables 410 -1 & 410 -2 or perform an arc hazard analysis to determine FR clothing requirements.

CP 2530 - Rule 431 C, Communication Antennas Prohibits workers from being exposed to radiation levels greater than those set forth by the administrative authority for 3 k. Hz < f < 3 GHz. OHSA 1910. 97, 1910. 268 IEEE Std. C 95. 1 -1999

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