I.B. 70A2580H02
Page 29
Effective November 2012
6-5 INSULATION
Type VCP-Wind 38kV Vacuum Circuit Breakers
primarily utilize epoxy insulation. 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 cleaning alcohol or commercial
equivalent. Secondary control wiring requires inspection
for tightness of all connections and damage to
insulation.
6-6 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 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.
6-7 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-Wind
circuit breakers do not
have sliding contacts at the moving stem. Instead they
use a highly reliable and unique flexible clamp design
that eliminates the need for lubrication and inspection
for wear.
Figure 6-2 Resistance Measurement Locations & Values Table
VCPW-Wind
