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 TM 5-684/NAVFAC MO-200/AFJMAN 32-1082
turer's instruction book for allowable overtravel. If
(a) If the primary contact gap required ad-
the specified overtravel is exceeded, the vacuum
justment, operate the circuit breaker several times
interrupter must be replaced because of excessive
to verify correct performance.
contact erosion.
(b) Check the operation and the clearance of
(b) Perform a high-potential test to check the
the trip armature travel, and release the latch in
condition of the vacuum. Consult the manufactur-
accordance with the appropriate instruction book.
er's instruction book for test value, or use 60 per-
Replace any worn or damaged parts disclosed by
cent of the final factory test value.
this operation.
(c) On stored-energy circuit breakers, oper-
(2) Other requirements. Follow appropriate re-
ate the circuit breaker slowly. By using the spring
quirements given for air circuit breakers.
blocking device, check for binding or friction, and
d. Metalclad switchgear. Inspect enclosure hous-
correct if necessary. Make sure contacts can be
ing, buses, and other switchgear members every
opened or closed fully.
time that circuit breakers are inspected. Supple-
(d) Reinstall box barriers and measure insu-
ment the following with the manufacturer's recom-
lation resistance of each bushing terminal to ground
mendations:
and phase to phase. Record resistance readings and
(1) Enclosure housing. The enclosure housing's
also temperature and humidity.
function is to eliminate personnel exposure to line
(3) Tests. Perform tests every 1 to 3 years de-
parts and to protect equipment from environmental
pendent upon the severity of duty encountered by
the circuit breaker.
(a) Establish a program to regularly lubri-
(a) Perform a hi-pot test on the circuit
cate hinges, latches, and locks and maintain enclo-
breaker bushings.
sure finishes.
(b) Check the c osed circuit breaker contact
1
(b) Outdoor assemblies require elimination
resistance.
of moisture. Check space heaters and fans and their
(c) Perform a power factor test.
thermostats for proper functioning. Ventilators
(d) Perform a corona test.
must be clear of obstructions and air filters require
(4) Final checks.
systematic cleaning. Check for roof or wall leaks
(a) Using the coupler, test operate the circuit
and for floor openings which may require sealing.
breaker both electrically and manually. Check all
(2) Buses. De-energize buses and ground in ac-
interlocks.
cordance with safety requirements. Inspection,
(b) Insert and operate the circuit breaker in
cleaning, tightening, and testing for buses are as
the switchgear cubicle. Watch for proper operation
necessary as for circuit breakers.
of the positive interlock trip-free mechanism. The
(a) Inspect the surface of all insulating mem-
circuit breaker should trip whenever it has not been
bers for damage before any cleaning or dusting, as
fully inserted, or whenever it is in the test position.
well as after cleaning. Damage caused by electrical
(c) Remove the circuit breaker from the
distress will usually be evident on the insulating
switchgear cubicle and check the primary discon-
surface as corona markings or tracking parts.
nect wipe. Refer to the appropriate instruction book.
(b) Inspect with special care the areas most
(d) Insert the circuit breaker into the
susceptible to tracking, corona, and thermal heat-
switchgear cubicle, ready for energization.
ing. These areas include splices and junction points,
c. Vacuum circuit breaker procedures. Direct in-
boundaries between adjoining insulators, between
spection of the primary contacts is not possible, be-
an insulating member and a grounded metal sur-
cause they are enclosed in vacuum containers. The
face, or bridging paths across insulating surface.
operating mechanisms are similar to the air circuit
Check also for electrical distress that can occur on
breakers, and may be maintained in the same man-
hidden surfaces, such as adjacent edges between
ner. It is not recommended that a vacuum circuit
upper and lower members of split bus supports or
breaker be operated more than 2,000 times without
on sharp edges in the switchgear that are not insu-
an inspection.
lated.
(c) Remove dust and dirt on both phase and
(1) Specific checks applying to vacuum circuit
ground buses by wiping with a dry, clean cloth or by
breakers. Checking for contact erosion and vacuum
vacuuming.
condition is made with the circuit breaker removed
(d) Check tightness of accessible bolted bus
from its switchgear cubicle.
joints by the calibrated wrench method. Refer to
(a) Close the circuit breaker and measure
manufacturer recommendations for proper torque
the spring plate overtravel. Consult the manufac-
8-11
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