Transcript 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.
• 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 PreStressed 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.