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CHANGES TO THE 2007 NATIONAL ELECTRICAL SAFETY CODE

CHANGES TO THE 2007 NATIONAL ELECTRICAL SAFETY CODE. Section 2, Definitions. Supporting Structure Definition: Relocates and revises the definition of “readily climbable supporting structure.” Combines “readily climbable” and “not readily climbable” under one definition.

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CHANGES TO THE 2007 NATIONAL ELECTRICAL SAFETY CODE

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  1. CHANGES TO THE2007 NATIONAL ELECTRICAL SAFETY CODE

  2. Section 2, Definitions • Supporting Structure Definition: • 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.

  3. Rule 013C, Inspection and Work Rules • Inspection rules and work rules in the current edition of the NESC shall apply to inspection of or work on all new and existing installations.

  4. Rule 018, Method of Calculation • Where calculations are required, the resultant value shall be rounded off to the nearest significant digit unless otherwise specified by the applicable rule(s). • Eliminates questions about whether such language as “shall be not less than” requires rounding up or rounding off. • Note: Rule 230A4 requires clearance calculations to be rounded up to match the decimal system used in the rule or table.

  5. 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.

  6. Rule 97G, Bonding of Communication Systems to Electric Supply Systems • Requires using a common grounding conductor or bonding separate grounding conductors where both electric supply systems and communications systems are grounded on a joint use pole (except where separation is required by Rule 97A). • Use to be a “should” rule.

  7. Rule 215C, Grounding of Circuits, Supporting Structures and Equipment. Non-Current-Carrying Parts. • Rules 215 C3- C6 new. • Moved the guy insulator requirements of Rule 279 to Rule 215. • All requirements for using guy insulators in lieu of grounding guys will be in one place. • Specific requirements for using insulators in lieu of grounding guys and span wires are added. • Rule 279 retains the strength requirements for guy insulators.

  8. Rule 217A1a,SupportingStructures, Protection ofStructures, Mechanical Damage • Moves the following from Note status to Rule status:“This rule does not require protection or marking of structural components located outside of the traveled ways of roadways or established parking areas.”

  9. Section 23, General Clarificationfor Neutral Clearances • Revises Rules and Tables to clearly indicate supply Rule 230E1 neutrals have different clearances from supply conductors 0-750 V. • Previously, some tables had separate categories for 230E1 neutrals and others included them within the0-750 V category.

  10. Rule 230B, Ice and WindLoading for Clearances • Retains the ice loading districts for determining clearances. • Retains General Loading Map (Figure 230-1) and Ice, Wind and Temperature information (Tables 230-1 &230-2) for clearances and inelastic deformation. • Changes “loading districts” to “loading zones.” • Appendix B created to explain.

  11. Table 232-2, Vertical Clearance of Equipment Cases, Support Arms, Platforms, Braces and URLP Above Ground, Roadway, Rail or Water Surfaces • Adds switch handles, platforms and braces to the 1st column. • Old FN1 is new FN6 and applied to category 1b (Driveways, Parking Lots and Alleys), column 2 (UGLP 0- 750V). • Old FN1b in new FN1 applied to category 1d (Spaces and Ways Subjected to Pedestrians…), column 2.

  12. Rule 234C3d(1), Clearances ofWires, Conductors, Cables &RLP from Buildings, Signs, Billboards, Chimneys, Radio and TV Antennas Tanks, etc. • Increased the clearance of service drop conductors over a roof (where not attached) from 8 feet to 10 feet. • Combined Exceptions 1 & 2 into one exception and rewrote for readability. • Retains the reductions formerly allowed in Exception 2.

  13. Rule 235G, Conductor Spacing: Vertical Racks or Separate Brackets • Allows attaching cabled secondary to an existing neutral bracket provided midspan clearances are maintained and the cabled secondary is kept away from the neutral to avoid chafing.

  14. 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.

  15. Revision of Sections 25, 26 & 27 • Begins incorporating the Reliability Based Method for determining structure loading. • New extreme ice and concurrent wind loading map (from ASCE 7) based on 50 year ice and wind events. • Provides a new formula for extreme wind loads. • Maintains the 60’ exclusion for extreme ice and concurrent wind and extreme wind loading. • Establishes a sunset date of July 31, 2010 for use of the “old” load factors and strength factors method.

  16. EXTREME WIND LOADING FORMULA • Load in pounds = 0.00256 (V2) (kZ) (Grf) ( I ) (Cf) (A) • 0.00256 =Velocity-pressure numerical coefficient • V2 = Basic wind speed in miles per hour (squared) • Kz = Velocity pressure exposure coefficient. This value is defined in Rule 250C1, Table 250-2. • Grf = Gust response factor defined in Rule 250C2. • I = Importance factor, 1.0 for utility structures and their supporting facilities • Cf = Shape factor from Rule 252B2. • A= Projected wind area in square feet

  17. Rule 261A3, Table 253-1,Table 261-1A, Fiber-Reinforced Polymer Structures • Addresses the strength requirements and the strength factors for fiberglass poles and crossarms.

  18. Rule 351C1 & 2, Location & Routing, Other Conditions • The 5 foot horizontal clearance will apply only to below ground pools. • Recommends that DB UG cable should not be installed directly under buildings or other structures (below ground pools) unless the structure is suitably supported to limit transfer of a detrimental load onto the cable.

  19. Rules 410A3 & 420I2;Tables 410-1 & 410-2 • Requires that by January 1, 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. • In lieu of performing an arc hazard analysis 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.

  20. Rule 420Q, 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 Subpart G OSHA 1910.268 Subpart R FCC Bulletin 65 IEEE Std. C95.1-2005

  21. QUESTIONS?

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