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50
High-potential tests
The next series of tests (vacuum integrity and
insulation) involve use of high-voltage test
equipment. The circuit breaker under test
should be inside a suitable test-barrier
equipped with warning lights.
Vacuum-integrity check
(using dielectric test)
A high-potential test is used to verify the
vacuum integrity of the circuit breaker. The
test is conducted on the circuit breaker with
its primary contacts in the OPEN position.
High-potential tests employ hazardous voltages.
Will cause death and serious injury.
Follow safe procedures, exclude unnecessary personnel and use safety
barriers. Keep away from the circuit breaker during application of test
voltages. Disconnect the split plug jumper from between the circuit
breaker and switchgear before conducting high-potential tests.
Vacuum interrupters may emit X-ray radiation.
Can result in serious injury.
Keep personnel more than six feet away from a circuit breaker under
test.
X-rays can be produced when a high-voltage is placed across two
circuit elements in a vacuum.
High-potential test voltages
The voltages for high-potential tests are
shown in Table 4: High-potential test voltages
on page 51.
Note: Do not use dc high-potential testers
incorporating half-wave rectification. These
devices produce high-peak voltages.
High-peak voltages will produce X-ray
radiation. DC testers producing excessive
peak-voltages also show erroneous readings
of leakage current when testing vacuum
circuit breakers.
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