Basler Electric BE1-11t - Manual (Page 85)

9424200995 Rev H 73
Breaker Failure (50BF) Protection
The breaker failure (50BF) element provides protection and security for the power system against failure
of the monitored breaker.
Element logic connections are made on the BESTlogic
™Plus screen in BESTCOMSPlus® and element
operational settings are configured on the Breaker Fail (50BF) settings screen in BESTCOMSPlus. A
summary of the logic inputs and outputs and operational settings appears at the end of this chapter.
BESTCOMSPlus Navigation Path: Settings Explorer, Protection, Current, Breaker Fail (50BF)
HMI Navigation Path: Settings Explorer, Protection, Settings Group x (where x = 0 to 3), Current
Protection, Breaker Fail 50BF
Element Operation
The 50BF element monitors the current to determine whether or not current continues to flow into a
faulted circuit after a circuit breaker has been directed to interrupt the circuit. In the event that current
continues to flow into the faulted circuit (after a defined period of time has elapsed sufficient for the
breaker to have interrupted the current), then the circuit breaker is considered to have failed, and steps
must be initiated to trip the next set of breakers upstream in the power system. Breaker failure protection
may be applied to any portion of the power system where failure of a circuit breaker to operate properly
could result in severe system damage or instability.
Contact Sensing
Before any relay output can occur, there must first be an initiating signal from external contacts. Two
possible initiating signals are either the 52 Breaker Fail Initiate (52BFI) signal or the 50 Breaker Fail
Initiate (50BFI) signal. Contact sensing circuitry allows the BE1-11t to monitor external contacts for the
presence of these signals.
Logic to start the breaker failure timer via the 52BFI input is provided with breaker status supervision.
Both the breaker status and the 52 BFI logic input must be true for the 52BFI logic input to cause a trip
condition. Information on setting up the breaker status logic can be found in the
Breaker Monitoring
chapter.
Control Timer
The control timer provides a window of opportunity for a breaker failure output. It improves dependability
by sealing in the initiate request to prevent stopping of a breaker failure timing if the tripping relay drops
out prematurely. The control timer is initiated by a 50BFI signal. Upon sensing the 50BFI transition from a
0 to 1 state, the control timer seals in the 50BFI signal for the duration of the Control Timer setting. If the
control timer expires and the 50BFI signal is still present, an alarm signal occurs. A control timer setting of
zero (0) disables the control timer seal-in function allowing the control timer to follow the 50BFI input.
ReTrip and Trip
Phase and neutral fault detectors monitor current in the phases and the ground current input. At least one
of these fault detectors must be picked up to start the breaker failure delay timer.
The adjustable delay timer allows current to decay after the breaker is tripped. The delay timer is initiated
when either the 52BFI input or the 50BFI input becomes true. When both signals are false, the breaker
delay timer is stopped.
ReTrip
The ReTrip output is true when the delay timer is actively timing. The delay timer can be stopped by either
the fast current detector or the Block logic input being asserted. In BESTlogicPlus, the ReTrip output can
be connected to other logic elements to annunciate the condition, control other elements in logic, and
start the fault recorder (logic element FAULTTRIG).
BE1-11t Breaker Failure (50BF) Protection