Page 38 I.B. 3A74792H08
Effective 09/2014
Figure 6-2 Rear Measurement for Contact Erosion
Being Made (Circuit Breaker Closed)
6-7 INSULATION
Type VCP-W and VCP-WR 38kV Vacuum Circuit
Breakers primarily utilize cycloaliphatic epoxy insulation
except, for example, the black insulating shrouds.
Insulation maintenance primarily consists of keeping all
insulating surfaces 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
Eaton 5581 2CA or commercial equivalent. Secondary
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
Figure 6-3 Graphical Representation of Contact
Erosion Measurement (Circuit Breaker Closed)
lead of the test machine to one of the poles of the
circuit breaker. Connect the remaining poles and
circuit breaker frame to ground. Start the machine
with output potential at zero and increase to the test
voltage. Maintain the test voltage for one minute.
Repeat for the remaining poles. Successful withstand
indicates satisfactory insulation 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. Successful withstand indicates
satisfactory insulation strength of the secondary
control circuit. Remove the shooting wire.
6-9 PRIMARY CIRCUIT RESISTANCE CHECK
Since the main contacts are inside the vacuum
chamber, they remain clean and require no
maintenance at any time. Unlike many typical circuit
breaker designs, VCP-W and VCP-WR circuit
breakers do not have
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