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Update of NESC Subcommittee #5 Activities

Overhead Delivery Issues. Update of NESC Subcommittee #5 Activities. 2004 APPA E&O Joseph Rempe, P.E. Principal Engineer T&D, Tacoma Power APPA Representative on SC5. What the NESC IS and What it is NOT. It IS a Performance Code – Set the minimum standard for operating performance.

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Update of NESC Subcommittee #5 Activities

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  1. Overhead Delivery Issues Update of NESC Subcommittee #5 Activities 2004 APPA E&O Joseph Rempe, P.E. Principal Engineer T&D, Tacoma Power APPA Representative on SC5

  2. What the NESC IS and What it is NOT • It IS a Performance Code – Set the minimum standard for operating performance. • It is NOT a design standard (ie. NEC) – It is not intended to be the design processes by which lines are designed. • A difficult act to maintain – the Nature of Engineers.

  3. Highlighted Proposed Changes for the 2005 NESC being considered by SC5 • Rule 250B – New Ice & Wind Loading Map • Rule 250C - 60 foot exclusion removed and Extreme Wind considered on all Distribution Structures. • New Rule 250D – Construction & Maintenance Loads

  4. Changes Cont. • Rule 261 - FRC (Fiber Reinforced Composite) acknowledged and accepted similar to Steel and Pre-Stressed Concrete. • Rule 277 – Insulator Strength • Section 25, 26, & 27 rewrite to reflect Reliability Based Design methodology of applying loads and structure strength.

  5. Rule 250B – Ice & Wind Loading • To include ASCE 7 Ice and Wind map. • Developed after the “Perfect Storm” crushed the NE and Eastern Canada • Cold Regions Research and Engineering Lab (CRREL) of the Army Corps of Engineers (Kathy Jones) & Bonneville Power Administration

  6. Rule 250B – Ice & Wind Loading Continued • Conductor Clearances is being addressed by Sub-Committee #4.

  7. Rule 250C – 60 foot exclusion • All wind data taken at 10m (33 ft.) [Can the current statement be defended in court?] • Larger Distribution Conductors and more Telecommunications attachments • Distribution Line Failures – typical rural line crossing over a hill: Bernoulli Effect • Most areas will not see the controlling load change from current practices for Grade C Construction.

  8. Rule 250C – Continued • Coastal areas are major exceptions. The rule change will limit wind pressure for Grade B design to withstand Class 2 hurricane strength winds. (Winds above this do major structure and vegetation damage that are not reasonable to design for) • Grade C max 15psi, Grade B max 22psi

  9. New Rule 250D – Construction and Maintenance Loads • Intent of new rule is to ensure a safe structure for workers to climb and/or work on from initial construction through replacement. • Rule 263A reference for Grade N construction

  10. Rule 261 - Fiberglass Reinforced Composite (FRC) Poles • The sub-committee has received a change proposal that supports the inclusion of FRC Poles in the same manner as Steel and Pre-Stressed Concrete Poles. • New ASCE Engineering Practice #104 for design using FRC Poles.

  11. Rule 277 – Insulator Strength • A presentation by ANSI C29 Committee to SC5 highlighted failure tests performed on Ceramic and NCI insulators. (Endurance factors need to be seriously considered when loading of Insulators.) • Sufficient concern was expressed by members of SC5 that a CP was created to address findings of ANSI C29 Committee. • Rule 253 would include new Rule 253B and new Table 253-3 for Support Hardware and Insulators.

  12. Section 25, 26, & 27 Rewrite • ANSI is developing a manual for designing structures following the Reliability Based Design (RBD) methodology for applying loads and selecting support structures and hardware. • To reflect the work of the RBD Task Force.

  13. Please Join Me on SC5! We have a chair open for you! History Stories Your input on the process A chance to visit Piscataway, NJ Contact Mike Hyland.

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