Page 42 - Nuclear Plant Journal - March April 2013
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Mastering
Breaker
Maintenance
By Gregory Lichty, Public Service
Electric and Gas Company and Dave
Davis, AZZ | NLI.
Gregory Lichty
Originally from Somerset, Pennsylvania,
Greg served 22 years in the US Navy,
retiring in February, 2003 as a Senior
Chief Electrician.
He began work
at PSEG’s Hope
Creek Nuclear
Generating Station
in February, 2003
as an Electrical
Maintenance
Supervisor which
was his primary
job for five years.
In February, 2008,
he was hired into
the Maintenance
Department’s
position of
Component Specialist for the station’s
air circuit breakers and motors. While
being a Component Specialist is his
primary job at Hope Creek, he still
supports Salem and Hope Creek’s
refueling outages in the role of an
Electrical Maintenance Supervisor.
He is an active participant in EPRI’s
Circuit Breaker User Group as well as
the Large Electric Motor User Group.
Greg graduated in June, 2000 with a
Bachelors of Science Degree in Business
Administration from the University of
New Haven, New Haven, Connecticut
and in June, 2010 he received an MBA
from Georgian Court University in
Lakewood, New Jersey.
Introduction
“The greatest victory is that which
requires no battle.” Sun Tzu wrote this
some 2,500 years ago in his famous
work, The Art of War. As with many
quotes attributed to Sun Tzu, we can
apply this same phrase or idea to topics
unrelated to actual war. When applied
to low voltage breaker maintenance, we
might declare, “The best way to perform
breaker maintenance is to eliminate the
need for it.”
Most nuclear plants in the US began
operation in the 1970s and 80s, took more
than a decade to construct, and were
designed using modern technologies of
the day. This means that any original
plant equipment was likely designed
in the 1950s or
60s. Changes in
equipment over the
last half-century may
not be quite as stark
for some mechanical
equipment (a six-
inch carbon steel gate
valve available today
isn’t all that different
from one installed
decades ago), but
for most electrical
and
electronic
equipment,
the
differences are like
night and day. To make this point, we
will focus on one common product
used in all nuclear plants - low voltage
circuit breakers used in AC and DC
applications.
Low Voltage Breakers &
Maintenance
Rated at 600 volts and below, the
largest of these breakers can carry up to
4,000 amps, but most breakers typically
have 800 to 2,000 ampere frame sizes.
A typical nuclear plant has roughly 300
of these breakers installed in switchgear.
The purpose of a circuit breaker in a
nuclear plant is to operate (start and stop)
electrical equipment, and in the event
of a fault, to break a circuit by opening
(tripping) and deenergizing the circuit to
protect the downstream load.
The tripping process requires
contacts to separate very rapidly under
high amperage levels and the mechanism
responsible for this operation is under
tremendous spring tension. Whether
performed manually or automatically,
tripping a low voltage breaker is a
fairly violent event from a mechanical
perspective. Even though circuit
breakers are in electrical systems, they’re
mechanical devices. There are numerous
bearings, bushings, springs, levers, arms,
and the entire assembly can be very
maintenance intensive.
The two biggest challenges to breaker
maintenance are the shrinking number
of skilled maintenance personnel and
scarcity of replacement parts, including
rebuild kits for legacy circuit breakers.
This is especially true for nuclear safety-
related applications. There are several
different strategies for maintaining circuit
breakers, but the main options are to use
in-house or outside resources, overhaul
(rebuild) the breakers on or off-site, and to
rebuild spare breakers when time permits
and swap them out during outages.
Whichever combination of variables is
chosen, this is an expensive endeavor.
Fast-forward to modern low voltage
breakers. Composite materials have
replaced most of the metal frame structure
and superior manufacturing techniques
and materials allow for a more compact
design; sometimes occupying half the
volume of the original circuit breaker.
Modern breakers have far fewer parts and
require less maintenance. So much less
maintenance, that a modern breaker may
not require an overhaul for forty years
and need only be cycled periodically to
redistribute the lubricant. It is important
to note that modern lubricants are far
superior to the grease used in legacy
breakers and grease hardening in legacy
breakers is the leading cause of breaker
failures.
A new industrial facility being built
today, including a new nuclear plant,
would use modern breakers installed into
modern switchgear. The smaller breakers
allow for more breakers per volume
of switchgear, so new plants will have
less switchgear. An older non-nuclear
industrial facility wishing to upgrade may
simply replace its switchgear allowing for
new breakers to be used. But most nuclear
plants consider replacing switchgear too
extensive of a modification. This is the
quandary faced by many nuclear plants;
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Nuclear Plant Journal, March-April 2013
