Update of NESC Subcommittee #5 Activities

2004 APPA E&OJoseph Rempe, P.E.

Principal Engineer T&D, Tacoma Power

APPA Representative on SC5

Overhead Delivery Issues

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.

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

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.

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

Rule 250B – Ice & Wind Loading Continued

• Conductor Clearances is being addressed by Sub-Committee #4.

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.

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

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

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.

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.

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.

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.