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TM 5-683/NAVFAC MO-116/AFJMAN 32-1083
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CHAPTER 2
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SWITCHGEAR ASSEMBLIES 600V OR LESS
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suring the resistance of contacts, ammeters,
2-1. Periodic Maintenance.
voltmeters, megohmmeters, low voltage/high cur-
A periodic maintenance schedule must be estab-
rent test sets for testing power circuit breakers, and
l i s h e d to obtain the best service from the
other special test equipment.
switchgear. Annual check should be made on all
(4) Manufacturer's instruction books regarding
major switchgear devices after installation. After
the maintenance of switchgear devices such as cir-
trends have been established regarding the equip-
cuit breakers, relays, bus bars, meters, etc. The
ment condition and reliability, the maintenance in-
fundamentals that are presented in the upcoming
terval may be extended (1836 months) in keeping
sections are designed to supplement these instruc-
with the operating conditions. A permanent record
tions, giving the elements of the overall mainte-
of all maintenance work should be kept. The record
nance program rather than the details.
should include a list of periodic checks and tests
2-2. Metal enclosures.
made (including date of test), condition of the equip-
ment, repairs or adjustments performed, and test
Maintenance is recommended below:
data that would facilitate performing a trend analy-
a. With power off and the bus properly grounded,
sis. Maintenance personnel must follow all recog-
open the enclosure and remove any accumulated
nized safety practices, both the nationally published
dust and dirt. Vacuum cleaning is recommended;
standards and military regulations. Some specific
blowing with compressed air is not.
suggestions in dealing with switchgear mainte-
b. Check structure and anchor bolts for tight-
ness. For bus and breaker connections ensure
nance are given below:
manufacturer's specified torques are used.
a. Tools designed for slowly closing switchgear
c. Clean and lubricate circuit breaker racking
circuit breakers or other devices during mainte-
mechanisms with a non-hardening, non-conductive
nance are not suitable for use on an energized sys-
grease.
tem. The speed necessary for device closing is as
d. Inspect operation and adjustment of safety
important as its speed in opening; therefore, a
shutters, mechanical and key interlocks, auxiliary
wrench or other manual tool is not fast enough.
and limit switches.
b. Before working on a switchgear enclosure,
e. Clean and inspect strip heaters.
verify that the enclosure is de-energized by check-
f. Clean any air filters that are installed in the
ing for voltage using a voltage detector.
ventilation openings.
c. Disconnect all drawout or tilt-out devices such
g. Inspect all relays, contractors, switches, fuses,
as circuit breakers, instrumentation transformers,
and other auxiliary devices for correct operation
and control power transformers.
and cleanliness.
d. Do not lay tools on the equipment while work-
h. Tighten control wiring connections.
ing. It is all too common to forget a wrench when
i. Inspect alignment and contacting of primary
closing up an enclosure. Don't take the chance.
disconnecting devices, checking for signs of abnor-
e. Never rely upon the insulation surrounding an
mal wear or other damage. Discoloration of these or
energized conductor to provide protection to person-
other silvered surfaces is not usually harmful un-
nel. Use suitable safety clothing and equipment.
less caused by sulphide deposits, which can be re-
f. Always use the correct maintenance forms and
moved by a solvent, such as alcohol, or silver polish.
equipment. When performing maintenance the fol-
lowing should be available:
j. After cleaning, measure the resistance to
(1) Forms for recording the conditions as found
ground and between phases of the bus with a
and work done.
megohmmeter (para 14-2). It is not possible to give
definite limits for satisfactory insulation resistance
(2) Control power connections, test couplers,
and spare parts recommended by the manufacturer
values, so that a change in the reading from one
to facilitate repair and maintenance of each type of
inspection period to another is the best indication of
circuit breaker.
any weakening tendency. The readings should be
taken under similar conditions each time, and the
(3) Special tools, such as lifting mechanisms
for removing and transporting power circuit break-
record should include temperature and humidity.
ers, relay test plugs for testing and calibrating pro-
k. Before replacing the breaker, wipe the primary
tective relays, a low resistance ohmmeter for mea-
disconnecting device contacts. Apply a thin coat of
2-1
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