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25
Installation
01.4IB.50032C
To check insulation integrity, the AC high
potential test described below is strongly
recommended. Using DC testing is not
the preferred method, however, values are
provided due to the availability of DC test
sets.
!
CAUTION
If DC high potential testing is performed,
the DC high potential test machine must
not produce instantaneous peak voltages
exceeding 50kV.
The circuit breaker insulation should be
tested with the circuit breaker vacuum
interrupter contacts in the CLOSED
position.
Test each pole of the circuit breaker
separately, with the other 2 poles and
the frame grounded. Perform the field
dielectric test described in ANSI Standard
C37.20.2, at the voltage level appropriate
for the equipment (
Table A Field Dielectric
Test Values
).
Table A Field Dielectric Test Values
Rated Maximum Voltage
(kV rms)
Power Frequency
Withstand (kV rms)
15
27
This test will have checked all of the
primary phase-to-ground and phase-to-
phase insulation.
!
CAUTION
After the high potential is removed, an
electrical charge may be retained by the
vacuum interrupters. Failure to discharge this
residual electrostatic charge could result in an
electrical shock. All six primary disconnecting
devices of the circuit breaker and the metallic
mid-band ring, if present, should be grounded
and remain grounded for at least on minute
to reduce this electrical charge before coming
into contact with the primary circuit.
!
CAUTION
Remove all grounding conductors applied
for this test before placing the circuit breaker
back into service.
The tests described in this section are the
only tests required to ascertain insulation
integrity. Because of the design of the
PowlVac
®
insulation system, no valid data
can be obtained utilizing other types of
high voltage insulation tests.
