Page 100 - Practical Power System and Protective Relays Commissioning

98 Practical Power System and Protective Relays Commissioning

FIGURE 7.14 Time measurement connection to measure the operating times of circuit breakers.

time—this device measures and records the time and timing diagram. The
test is done at 100% of voltage substation DC voltage and 80% of voltage
substation DC voltage, as well as at 60% of voltage substation DC voltage
and at 80% there should be no any pole discrepancy in three-phase closing
and three-phase tripping.
The obtained close/open time should be compared with the
manufacturer’s reference values or factory test results. Refer to Fig. 7.14 for
CB timing tester connection to measure the operating times of CB.

7.6.5 Reduced Voltage Test

This test is carried out to confirm the operation of the closing coil of the cir-
cuit breaker when reducing the control dc voltage of the circuit breaker. A
reduced voltage of 80% of the rated voltage for the closing coil and 60% of
the rated voltage for the trip coil at these two values of the voltage the
breaker should be able to operate (close and open).