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MAINTENANCE
CRITERIA:
1. If a current flow above 5 milli-amperes is
observed or if breakdown occurs, one or
more of the interrupters has insufficient
vacuum and must be replaced.
Exception:
If the current exceeds 5 milli-
amperes the first time the voltage is brought
up, reduce the voltage to zero and increase it
again. It may be necessary to repeat this
procedure a few times.
2. If the contactor fails to meet criteria 1, then
repeat the test on each pole separately to
identify the damaged interrupter or
interrupters.
3. If the voltage can be held for 1 minute and
the current flow does not exceed 5 milli-
amperes, the interrupter has a sufficient
vacuum level.
After the test is complete, discharge any residual
static charge from the primary terminals of the
circuit breaker.
If a vacuum checker or AC hi-pot tester is not
available, a DC hi potential test may be
conducted. If a DC test is conducted, the test
voltage must be increased to 14kV DC. The test
duration for DC tests and the criteria for
acceptance remain the same as for AC tests.
Do not use DC hi-pot
testers which employ
unfiltered half-wave
rectifiers. The peak
voltages produced by these
testers may exceed the
recommended value of
14kV. This can result in the
production of harmful X-
rays and may invalidate the
test results.
Figure 12 - Application of Test Voltage for
Vacuum Check
1 minute
10kV AC
(14kV DC)
Voltage
Zero
10 sec
10 sec
Time
WARNING
