
CBF-Supervision Module – Circuit Breaker Failure Protection [ANSI 50BF]
Commissioning: Circuit Breaker Failure Protection [ANSI 50BF]
The time that is parameterized for the
CBF
must not be below the CB
control time, otherwise an unwanted operation of the
CBF
is caused by any
protective trip.
Object to be tested
Test of the circuit breaker failure protection.
Necessary means
•
Current source
•
May be: ampere meter
•
Timer
When testing the applied test current must always be higher than the
tripping threshold
»I-LSV«
. If the test current falls below the threshold while
the CB is in the OFF-position, no alarm will be generated.
Procedure (single-phase)
For testing the tripping time of the CBF protection a test current has to be impressed which is higher than the
threshold value of one of the current protection modules. When the trip relay that is assigned to the protection
function, picks up, a timer will be started and the time until the CBF is signaled by the corresponding relay will be
measured.
To avoid wiring errors, it should be checked, if the CB in the higher-level system switches off.
The time, measured by the timer, should be in line with the specified tolerances. Alternatively the timer can be
started when the auxiliary voltage is applied and the test current impressed and then stopped when the relay for
the CBF protection picks up. In this case, the previously measured tripping delay has to be subtracted from the
measured time.
Re-connect the control cable to the circuit breaker!
Successful test result
The actual times measured comply with the set-point times. The CB in the higher-level section switches off.
Page 452
EN MRA4 04/09
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