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4
IB 6.2.7.7-3
the required test voltage cannot be sustained
across
the
open
contacts
interrupter, the interrupter may be faulty and must
be replaced. Always insure that the contact air
gap is correct before conducting primary circuit
dielectric tests.
WARNING
Do not run any primary circuit dielectric withstand
tests on isolated interrupters with open contacts
above rated voltage, unless test personnel are
adequately shielded or are no less than six feet
from the test unit.
WARNING
If the circuit breaker has been energized, or it is
unsure if the circuit breaker has ever been
energized,
the
mid-band
interrupters so equipped) must first be discharged
before any work is performed on or near the
interrupters. A grounding stick must be used to
discharge the ring by fastening the ground cable of
the stick to known ground, and touching the
grounding tip of the stick to each mid-band ring.
Note the following:
• Dielectric test voltages higher than rated voltage,
applied across open contacts, may cause a
vacuum interrupter to emit some X-radiation,
which could be a health hazard on prolonged
exposure at close range.
though the emission is low, it is considered
appropriate to exercise caution. Therefore, do
not run any primary circuit dielectric withstand
tests on isolated interrupters with open contacts
above rated voltage unless test personnel are
adequately shielded or they are no less than six
feet from the test unit.
• It is to be noted that no hazardous X-radiation is
produced with closed contacts at any test
voltage, nor with open contacts at rated voltage,
and there should be no cause for concern. If
the breaker is tested in its compartment at the
test voltages recommended below, the steel
enclosure will provide sufficient shielding to
protect personnel from X-radiation at the normal
distances maintained for electrical safety.
of
the
vacuum
ring
(on
vacuum
Accordingly, even
NOTE: Only an AC hi-pot test is recognized as a
valid test. DC, Meggers, etc. are not valid for hi-
pot testing.
The following test values should be used for
dielectric testing the new breaker, and are to be
applied for a one-minute period:
• Primary Circuit, new interrupters
36kV for 7.5kV and 15kV
19kV for 5kV
• Secondary Circuit
1100VAC (except motor)
540VAC (motor)
Once in service, the different circuits should be
tested at 75% of these ratings.
If it is desired to make a dielectric test on the
secondary control wiring, turn the spring charging
Motor Disconnect Switch to the "OFF" position.
Apply test voltage (1100VAC) for one minute to
each of the secondary contacts of the circuit
breaker.
If it is desired to make a dielectric test on the
spring charging motor, turn the Motor Disconnect
Switch to the "ON" position. Apply test voltage
(540VAC) for one minute to the motor circuit.
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