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Marne and Associates NESC and OSHA Newsletter
addresses issues relevant to power and
communication utilities.
In This Issue:
Question #1:
Is it true that
a TIA is changing the Arc Rated Clothing tables
in the NESC?
A Tentative Interim
Amendment (TIA) has been proposed to make
changes to NESC Table 410-2 and is scheduled for
vote on September 5. The TIA could pass as
written, be delayed for further comments, or be
rejected. We will keep you updated via this
newsletter when we find out the TIA status. When
approved, a TIA is associated with the current
edition of the NESC and is considered a change
proposal for the next edition.
Fig. 1
shows an example of arc rated clothing. For more
information please consider our live web seminar
which is offered once a month from August to
December on the subject of Arc
Flash Hazards and Arc Rated Clothing.
Photo
Courtesy Salisbury
Fig. 1 -
Jacket Rated for 11
cal/cm2
Question #2:
I heard that 40
inches was the required clearance from
communication attachments to the power above,
but the power utility is telling me I need more
than 40 inches because the power line operates
at 24.9kV. Doesn't the NESC require 40
inches?
The communication
worker safety zone does have a "base" value of
40 inches; however, this value is dependant on
the voltage involved. NESC Tables 235-5 and
238-1 require an additional 0.4 inches to be
added for every kV above 8.7 kV. For the
24.9/14.4 kV line referred to in the question,
the NESC would require a communication worker
safety zone of
40in + (14.4kV - 8.7kV) *
0.4 in/kV = 43 in
The phase-to-ground
voltage (14.4kV) is used in this example as it
is assumed that the 24.9/14.4kV line is
effectively grounded. The result is rounded up
to the nearest inch as required by NESC Rule
230A4. We discuss this and other issues in
detail in the NESC
Rules for Joint Use Construction 2-day
seminar.
News and Upcoming Events:
NESC Rules
for Joint Use Construction
More
info.
Coming to Dallas,
TX (Sept 16-17); Atlanta, GA (Nov 12-13); and
Missoula, MT (Dec 3-4).
This NESC®
seminar is a two-day class focusing on the joint
use construction rules in the National
Electrical Safety Code® (NESC®). The class will
provide an overview of each part of the NESC®
that deals with joint use construction (Day 1).
Applying the Code to day-to-day work will be
stressed by focusing on practical applications
and class attendee questions (Day 2). The class
includes ample time for questions and attendees
are encouraged to share their NESC® applications
with the class. The presentation is rich in
graphics. More
info.
Arc Flash
Hazards and Fire Rated Clothing
More
info.
Need help meeting
the Jan 1, 2009 deadline for the NESC® arc flash
rules? Join our 90-minute live web seminar which
is offered once a month from August to December.
More
info.
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