Maintenance
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 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 test voltages
The voltages for high-potential tests are shown in Table 3: 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.
