Woodward highprotec MRI4, User Manual

Page: 557 / 727

Supervision
Supervision
CBF- Circuit Breaker Failure [50BF*/62BF]
*=only available in protective relays that offer current measurement.
Available elements:
CBF
Principle – General Use
The breaker failure (BF) protection is used to provide backup protection in the event that a breaker fails to operate
properly during fault clearing. This signal is to be used to trip the upstream breaker (e.g. infeed of a busbar) either
via an output relay or via Communication (SCADA). Depending on the ordered device and type there are
different/multiple schemes available to detect a breaker failure.
Start/Trigger of the CBF Timer
A supervision timer »
t-CBF« will be started, once the CBF module is triggered. Even if the Trigger signal drops
again, this timer will continue to run. If the timer runs down/elapses (is not stopped), the module will issue a trip
afterwards. This trip signal is to be used to trip the upstream breaker (backup).
Stopping the CBF
The timer will be stopped if the opening of the breaker is detected. Depending on the supervision scheme the timer
will be stopped if the current falls below the current threshold or if the position signals indicate the open position of
the breaker or a combination of both. The
CBF module will remain within the state rejected until the trigger signal
drops (falls back).
Detecting a Breaker Failure
Depending on the supervision scheme, the Circuit Breaker Failure signal (Trip) will be set if either:
the current doesn´t fall below the threshold or
the position signals indicate that the breaker is in the closed position or
both.
Reject state of the CBFmodule
The
CBF module will switch into the rejected state if the circuit breaker failure triggers are still active while the open
position of the breaker has been detected successfully.
Readiness for Operation
The
CBF module will switch back into the Stand-by if the trigger signals drop (fall back).
Locking
A locking signal will be issued simultaneously with the
CBF-Signal (Trip). The locking signal is permanent. This
signal has to be acknowledged at the HMI.
557 MRI4 DOK-HB-MRI4-2E