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Preventative maintenance is not a new
concept. People have been doing
precautionary work on motors, engines, and
other mechanical systems for decades.
According to the Institute of Electrical and
Electronics Engineers (IEEE), the failure
rate of electrical components is three times
higher for systems where preventive
maintenance is not performed. This tells us
that electrical failures, for the most part,
can be avoided.
A great deal can go wrong if an
electrical distribution system is not
adequately maintained. As electrical loads
cycle between high and low demand, thermal
expansion and contraction cause connections
to loosen. Electrical panels that are never
cleaned accumulate dust and dirt that
deposit on these connections. The loose and
dirty connections provide a high resistance
path that are directly responsible for more
than 30 percent of electrical failures.
Another 17 percent of electrical failures
are attributed to live electrical components
being exposed to moisture.
An EPM program should be performed on a
regular basis. The period between work
depends on the environmental conditions, the
importance of the equipment and its loading
and use. However, EPM should be performed at
least once every three years — and more
often for critical components.
The first step in an EPM program is a
complete thermographic inspection of all
electrical equipment prior to the scheduled
outage. This survey is a non-invasive method
of identifying high temperature excursions
which indicate potential problem areas due
to loose or dirty connections, load
imbalances, or improper installation of
equipment. This initial step helps in
determining the resources you will need
during your scheduled outage to perform EPM.
Ideally, a thermographic inspection should
be done during peak-load conditions by a
certified, experienced thermographer.
Plans should be made to have all circuit
breakers and disconnect switches repeatedly
opened and closed during the shut-down
period to ensure proper operation. In
addition, protective relays and circuit
breaker trip devices need to be tested and
calibrated on a regular basis. Different
test sets are often required for the various
equipment depending on the manufacturer and
the age of the devices. Therefore, ensure
that the people doing this work have the
proper equipment, experience, and training
to perform these functions.
Electrical preventive maintenance is
cost-effective in several different ways.
First, it is cheaper to make repairs to
equipment before it fails. When electrical
equipment fails, particularly protective
devices like circuit breakers or relays,
there is usually subsequent damage to other
components in the system. Often the
equipment cannot be repaired and must be
completely replaced. New equipment does not
always replace the failed component in-kind
and may require other modifications to make
the system whole.
Failed equipment results in unplanned
outages that can be very costly when
replacement equipment cannot be easily
found. Instead of having a planned system
outage for EPM at the most convenient time
for your operation, equipment failures are
always at inopportune times. Emergency
repairs are very costly due to the urgency
of the situation where temporary work is
required before a permanent repair can be
done.
In addition, an effective EPM program
will improve equipment efficiency and reduce
utility bills. A loose or dirty connection
has increased resistance which results in
higher power losses. By simply tightening
and cleaning electrical connections, you can
lower these energy costs. When considered
over a period of time, these energy losses
can add up to quite a significant amount of
money. |
