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| Photo 1 |
| An example of violation and hazard created by a corroded steel electric meter socket |
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IAEI
News>Issue Listing>May/June 2003 >Other Code—Inspection of Lines and Equipment
Other Code
Inspection of Lines and Equipment |
To insure that electric supply facilities comply with the rules of the National Electrical Safety Code (NESC), Rule 214A 2 states, "Lines and equipment shall be inspected at such intervals as experience has shown to be necessary." What does this mean? How frequent is "…intervals as experience has shown to be necessary"? To understand this rule, we need to talk about the limitations of inspection in identifying NESC violations and averting electrical contact accidents. |
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To insure that electric supply facilities comply
with the rules of the National Electrical Safety Code (NESC),
Rule 214A 2 states, "Lines and equipment shall be
inspected at such intervals as experience has shown to
be necessary." What does this mean? How frequent is
"…intervals as experience has shown to be
necessary"? To understand this rule, we need to
talk about the limitations of inspection in identifying
NESC violations and averting electrical contact
accidents.
Material Failure
The materials used to construct electric supply
facilities deteriorate over time. Deterioration of these
materials can create violations of the NESC and hazards
to the public. Metal enclosures like electric meter
sockets located in salt fog environments typically near
ocean beaches often corrode to the point of developing
holes. The following photograph is an example of
violation and hazard created by a corroded steel
electric meter socket. The socket was located about a
hundred feet off an ocean beach. The socket was still
energized when I took the picture and was located only
three feet off a sidewalk where hundreds of people walk
to the beach every day. The holes in the enclosure did
not develop overnight. If the utility who owned the
socket found from experience that it takes a minimum of
four years for holes to develop after the initial signs
of corrosion, then it would be appropriate for that
utility to inspect their steel meter sockets located in
that environment at least every four years as long as
they replaced the sockets showing signs of corrosion
within the four-year period after inspection.
Photo 1
Utility Poles
The strength of wood utility poles deteriorate with
time. The structure loading and strength requirements of
the NESC in Sections 25 and 26 define when a pole shall
be replaced. When considering ice and wind loading of
Rule 250B and using the overload factors of Table 253-1
and the strength factors of Table 261-1A, the NESC in
footnote 2 of Table 261-1A (page 182) requires wood
poles to be replaced or rehabilitated when deterioration
reduces the structure strength to 2/3 that required when
installed. When considering the extreme wind loading of
Rule 250C, footnote 3 of Table 261-1A requires wood
poles to be replaced or rehabilitated when deterioration
reduces the structure strength to ¾ that required when
installed. Allowing pole strength to deteriorate below
the minimum set by the NESC not only creates a violation
of the rules, it also creates hazard to the public if
the pole breaks. Some utilities and contractors have
developed non-destructive test methods for predicting
the strength of wood poles in the field. These methods
can be used to identify poles for which the strength has
deteriorated. If a utility tests its poles and replaces
deteriorated poles on a eight-year cycle and finds that
they experience very few pole failures under anticipated
loading conditions, then experience has shown that an
eight-year pole inspection cycle is appropriate.
Electrical Contact
Accidents
Most electric supply contact accidents involving the
public are not a result of anything to do with
deterioration of the utilities facilities. Most
accidents involving electric utility facilities are the
result of people working too close or constructing
buildings and other structures too close to energized
conductors. Constructing buildings and other structures
so close to electric supply facilities that the
clearance between the building and the line is less than
that required by Rule 234 (page 96) of the NESC is a
clear violation of the rules of the NESC and a hazard to
the construction and maintenance personnel. One would
think that the OSHA regulations and the fear of
electrocution would stop people from approaching
electric power lines. That is not enough.
In an attempt to stop the fatalities, most states have
now made it illegal to approach high voltage electric
power lines. Those laws are usually called "High
Voltage Line Safety Acts." To learn more about
these laws and the OSHA regulations, see my March/April
2000 article, "Working in Dangerous Proximity to
Overhead High Voltage Lines—OSHA, NESC, and the
Law." Even with the OSHA regulations and the state
laws, the dangerous actions continue. The brick masons
who decide to re-point the brick building with a metal
aerial lift, the sign company who decides to install a
new store sign directly beneath the power line, the
painters who decide to paint a house with aluminum
ladders crossing under the power line, the industrial
plant that decides it needs to construct a large storage
tank under the power line, the house builder who decides
to build a house under a power line, are all examples of
the types of accidents that occur on a daily basis
around the country.
Would regular scheduled inspections catch these
situations? No, not unless they were very lucky. That is
not to say that none is averted by utility employees
while they are doing other work. Most utilities have a
lot of employees in the field on weekdays. Often these
employees, police officers and people from the public do
catch dangerous actions before they become fatal ones.
It is this type of inspection the NESC is referring to
in the note following Rule 214A 2, "It is
recognized that inspections may be performed in a
separate operation or while performing other duties, as
desired." Most utilities encourage their field
employees to look for dangerous conditions and actions
by the public. That does not mean that every utility
employee in the field has the time or the knowledge to
recognize a dangerous condition or action. There are
some electric utility employees that have no more
knowledge of the hazards associated with electric power
lines than the general public. It is unreasonable to
expect all electric utility employees to be responsible
for identifying dangerous actions and conditions.
If you have general questions
about the NESC®, please call me at 302-454-4910 or
e-mail me at dave.young@conectiv.com .
National Electrical Safety Code® and NESC® are
registered trademarks of the Institute of Electrical and
Electronics Engineers.
Dave Young is a senior project engineer with Conectiv Power
Delivery of Wilmington, Delaware, where he has been
working with and teaching the NESC® for over 31 years.
He is a member of the NESC Interpretations Subcommittee
and represents the Edison Electric Institute on the NESC Overhead Line Clearances Subcommittee 4.
Dave is also vice-chairman of the Delmarva Division of
the IAEI Chesapeake Chapter.
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