PROPOSED CHANGES TO THE2007 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 94B7, 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 4th edition values.

• Appendix B

CP 2508- Rule 230, Uniform Clearance Calculations

Wind loading values revert to 4th 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 232B3, 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 (V2) (kZ) (Grf) ( I ) (Fg) (Cd) (A2)

• 0.00256 = Ambient air density value• V2 = 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 252B2 (Rules N251A & 251B).• A2 = Projected wind area squared in square feet

CP 2766- Rule 250C, EXTREME WIND

Limits extreme loading on structures < 60’.

• Limits 0.00256V2kZGRF to 15 psf for Grade C.

• Limits 0.00256V2kZGRF to 30 psf for Grade B.

CP 2658- Rule 250D, 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 261A3, Table 261-1A, Fiber-Reinforced

Polymer Structures

Addresses the strength requirements and the strength factors for fiberglass poles and crossarms.

CP2622- Rule 351C, 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/cm2, FR clothing shall be worn.

• For V < 1000V, FR clothing with a min resistance of 4 cal/cm2 shall be required.

• For V > 1000V, use Tables 410-1 & 410-2 or perform an arc hazard analysis to determine FR clothing requirements.

CP 2530- Rule 431C, Communication Antennas

Prohibits workers from being exposed to radiation levels greater than those set forth by the administrative authority for 3 kHz < f < 3 GHz.

OHSA 1910.97, 1910.268IEEE Std. C95.1-1999

QUESTIONS?