I.B. 3A74792H04
Page 31
Effective 7/97
6-7 INSULATION
Type VCP-W 38kV Vacuum Circuit Breakers primarily
utilize cycloaliphatic epoxy insulation except, for exam-
ple, the black insulating shrouds. Insulation mainte-
nance primarily consists of keeping all insulating sur-
faces clean. This can be done by wiping off all insulating
surfaces with a dry lint free cloth or dry paper towel. In
case there is any tightly adhering dirt that will not come
off by wiping, it can be removed with a mild solvent or
distilled water. Be sure that the surfaces are dry before
placing the circuit breaker in service. If a solvent is
required to cut dirt, use Stoddard’s Solvent Cutler-
Hammer 55812CA or commercial equivalent. Second-
ary control wiring requires inspection for tightness of all
connections and damage to insulation.
6-8 INSULATION INTEGRITY CHECK
Primary Circuit:
The integrity of primary insulation may be checked by
the 60Hz AC high potential test. The test voltage
depends upon the maximum rated voltage of the circuit
breaker. For circuit breakers rated 38kV the test voltage
is 60kV rms. Conduct the test as follows:
Close the circuit breaker. Connect the high potential
lead of the test machine to one of the poles of the circuit
breaker.
Connect the remaining poles and circuit break-
er frame to ground. Start the machine with output poten-
tial at zero and increase to the test voltage.
Maintain the
test voltage for one minute.
Repeat for the remaining
poles. Successful withstand indicates satisfactory insu-
lation strength of the primary circuit.
If a DC high potential machine is used, make certain
that the peak voltage does not exceed the peak of the
corresponding AC rms test voltage.
Secondary Circuit:
Connect all points of the secondary terminal block with
shooting wire. Connect this wire to the high potential
lead of the test machine. Ground the circuit breaker
frame. Starting with zero, increase the voltage to 1125
volts rms. Maintain the voltage for one minute. Suc-
cessful withstand indicates satisfactory insulation
strength of the secondary control circuit. Remove the
shooting wire.
Figure 6-2 Rear Measurement for Contact Erosion
Being Made (Circuit Breaker Closed)
Figure 6-3 Graphical Representation of Contact Erosion
Measurement (Circuit Breaker Closed)
Base of Interrupter
Standard 12 inch
Metal Scale
Inch
Measurement Line
Summary of Contents for Cutler-Hammer VCP-W
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