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Institute for Crisis, Disaster, and Risk Management Crisis and Emergency Management Newsletter Website |
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December
2003
Volume 5
- Number 3 |
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Related Sites:
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Prioritization
of Power Restoration by Laura
Rabb (My
original assignment was to chart power outages in the DC Metro area
over the
last 2 years. However, the information
is not available on their web sites and after leaving both voice mails
and
e-mails with all three power companies, only Dominion replied to let me
know
that they do not provide that information to the general public.) Potomac
Electric Power Company (Pepco), Dominion Virginia Power (Dominion), and
Baltimore Gas and Electric (BGE) are the three power companies in the
DC Metro
area. Pepco serves DC and most of
Montgomery and According
to the BGE web site (www.bge.com),
more than 70% of power outages are caused by
weather. The second most common cause,
at 11%, is animals contacting wires. The
Pepco web site (www.pepco.com)
indicates that other causes include digging,
traffic accidents, equipment failures and pre-scheduled utility
maintenance. Many outages are what Pepco
calls “momentaries”. This are
split-second losses in power often caused when automatic sensing
equipment
detects a dangerous situation and temporarily breaks the flow of
electricity. The outage is often long
enough to require you to reprogram your VCR, clock radio, microwave,
etc. The
computer system at Pepco prioritizes system outages, based on
established
guidelines, to correct potentially life-threatening situations and to
get power
to the largest numbers of customers. Outages
are grouped along the same circuit or feeder lines
to analyze
the probable cause and assign appropriate resources.
The first priority is given to
life-threatening situations, such as downed live wires and hospitals
without
power. The next priority is to restore
power to the largest number of customers at one time by focusing on
repairs to
substations and major feeder lines. They
then work to restore power to smaller groups of customers or
neighborhoods. The last priority is to
individual homes and businesses. (www.pepco.com)
Dominion
and BGE have priority systems similar to Pepco. Hospitals,
other medical facilities, public safety
facilities (911,
rescue, police, fire), and water treatment plants are given top
priority. Downed live wires were not
mentioned by
either company, but I would hope they are also given top priority. The next priority is to repair main power
lines and equipment to restore power to the greatest number of
customers in the
shortest amount of time. It would not
help to repair an individual problem until the larger lines and systems
are
restored, so individual homes and businesses are the last priority. (www.dom.com, www.bge.com) The following is information on the amount of customers that may be affected by a part of the system being damaged and is an indication of the restoration priorities by all three companies. Transmission lines bring bulk power from power plants and connect to several substations. A downed transmission line may affect more than 10,000 customers. Substations distribute power to several circuits and a problem at a substation can cut power to more than 6,000 customers. Distribution lines form power networks connecting communities and industries. A downed distribution line could affect more than 1,500 customers. Overhead lines serve smaller customer groups or neighborhoods and affect more than 50 customers. Transformers reduce voltage to homes or businesses. A damaged transformer affects less than 10 customers. (www.bge.com)
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