Section 8. Maintenance - GE PVDB-28kV Instructions Manual

Distribution Breaker
Section B. Maintenance
8-12 Primary Insulation Parts
Using dry non-linting cloth or industrial-type wipers,
clean accessible insluation surfaces on the intemlpter
supports and operating rod insulators. In seIVice
locations where contamination is heavy or external
flashovers have occurred during intemlpter high-
potential testing, clean the inside surface of the
intemlpter supports and the outer surface of the
PowerVac interrupters. Remove the interrupter
assembly, if necessary, per the procedure in REPAIR
AND REPLACEMENT (Section 9) and be sure to
discharge the interrupter midband ring (if present)
before removing the inteITupter assembly. Removal and
re-installation of intemlpter assemblies will normally not
require readjustment due to the design of the
intemlpter operating rod insluator connection. They
ShO1Ud be reulrned to the same location from which
they were removed.
8-9 Primary Circuit Resistance
A resistance check of the primary circuit may be made
with the breaker closed. Use a low resistance measuring
instnlment which measures microhms. The 100 ampere
reading sholud not exceed 90 microhms when
connected across the primary bars on the breaker.
8-13 Lubrication
Proper lubrication is important for maintaining reliable
circuit breaker performance. The ML-I 8H mechanism
used bearings which have a synthetic lining in some
locations. These bearings do not require lubrication to
maintain low friction, but ltlbrication does not harm
them and oiling lightly is recommended. Sleeve
bearings are used in some linkage locations and needle
or roller bearings are used for low friction on trip shaft
and close shaft.
8-10 Po wer Factor
The overall GST test can be performed on the bushing
of vacuum distribution circuit breakers in the same
open-breaker test procedure used for oil circuit breaker.
These tests are rated on the basis of dielectric-loss. The
power factor for each bushing of porcelain design is
tested at room temperaUlre, 23 degrees C, and should
not exceed 3%.
Power factor testing of the vacuum interrupter is not
recommended because of the low charging currents.
The Watt-loss measurement across the open vacuum
interrupter bottle is not meant to be a direct measure of
the dielectric-breakdown strength of the interrupter.
While defective bottles with improper vacuum or high-
loss conditions on the internal or the external surfaces
have been detected, separable identification is not easy
and the readings have not proven to be consistent.
Bearings are lubricated dllring factory assembly with
grease and oil, but all hlbricants have a tendency to
deteriorate by oxidation or contamination with age.
Providing a fresh lubricant supply at periodic intervals is
essential to proper breaker operation, especially where
frequent operation may have forced lubricantOllt of the
bearing surfaces. Apply a few drops of light synthetic
machine oil such as Mobil I at each bearing. Apply a
coat of 0282A2048POO9 on the four corners of the
closing spring gtlide where it enters inside the spring.
Electrical primary contact surfaces also require periodic
hlbrication to inhibit oxidation and minimize friction.
At each inspection and maintenance interval, the metal
contact surfaces of the movable contact rod of the
intemlpter ShO1Ud be lubricated with 0282A2048POO9.
This grease is available packaged in a pint can to
provide cleanliness and prevent oxidation.
For accurate verification of the loss of vacuum integrity
in a bottle, perform an AC hi-potential test as described
in section 8-8.
8-11 Mechanism
Check all items on Table 2, Summary of Adjustments
and Critical Dimensions, re-adjusting or tightening as
required. Lubricate as recommended under LOB-
RICAT!°N (para 8-13).
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