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Figure 7-4 Typical "T" Contact Wipe Indicator
7-6 INSULATION
In VCP-WR breakers, 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 breaker
in service. If a solvent is required to cut dirt, use
Stoddard's Solvent Cutler-Hammer 55812CA or
commercial equivalent. Secondary control wiring
requires inspection for tightness of all connections and
damage to insulation.
7-7 INSULATION INTEGRITY CHECK
Primary Circuit:
The integrity of primary insulation may be checked by
the AC high potential test. The test voltage depends
upon the maximum rated voltage of the breaker. For the
breakers rated 5 kV, 12 kV, 15 kV and 27 kV the test
voltages are 15 kV, 21 kV, 27 kV and 45 kV rms
respectively.
I.B. 8295A61H07
Conduct the test as follows:
Close the breaker. Connect the high potential lead of the
test machine to one of the poles of the breaker. Connect
the remaining poles and breaker frame to ground. Start
the machine with output potential at zero and increase to
the test voltage. Maintain the test volt-age 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:
Isolate the motor by disconnecting two motor leads
provided for this purpose. Connect all points of the
secondary terminal block with a shooting wire. Connect
this wire to the high potential lead of the test machine.
Ground the breaker frame. Starting with zero, increase
the volt-age to 1500 volts rms. Maintain the voltage for
one minute. Successful withstand indicates satisfactory
insulation strength of the secondary control circuit.
Remove the shooting wire and reconnect the motor
leads.
7-8 PRIMARY CIRCUIT RESISTANCE CHECK
Since the main contacts are inside the vacuum chamber,
they remain clean and require no maintenance at any
time. Unlike most typical circuit breaker designs, VCP-
WR breakers do not have sliding contacts at the moving
stem either. Instead they use a highly reliable and unique
flexible clamp design that eliminated the need for
lubrication and inspection for wear.
If desired, the DC resistance of the primary circuit may
be measured as follows: close the breaker, pass at least
100 amps DC current through the breaker. With the low
resistance instrument, measure resistance across the
studs on the breaker for each pole. The resistance
should not exceed the values shown in Table 7.2.
Table 7.2 Typical Resistance Measurements
For more information visit:
www.EatonElectrical.com
Effective: February 2007
Rated Continuous
Current (amperes)
600
800
1200
1600
2000
Instruction Book
Page 45
Resistance
(microohms)
46
39
39
26
26
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