Siemens SIPROTEC 4 Manual page 239

Criteria
Address 7004 Chk BRK CONTACT establishes whether or not the breaker auxiliary contacts connected via
binary inputs are to be used as a criterion for pickup. If this address is set to ON, then current criterion and/or
the auxiliary contact criterion apply. This setting must be selected if the breaker failure protection is started by
functions, which do not always have a certain criterion for detection of an open circuit breaker, e.g. voltage
protection.
Single-Element Breaker Failure Protection
In single-element breaker failure protection, the adjacent circuit breakers, i.e. the breakers of the busbar or the
busbar section affected, and where applicable also the breaker at the remote end, are tripped after the time
delay TRIP-Timer (address 7005) has elapsed. The time 50BF-2 Delay (address 7008) is in this case set to
infinite because it is not needed.
The time delay to be set should be based on the maximum circuit breaker operating time plus the dropout
time of the current flow monitoring element plus a safety margin which takes into consideration the tolerance
of the time delay. In case of an external start, the set time delay is reduced automatically by 10 ms in order to
compensate the residual time of the external start.
[abl-bei-norm-fehlerkllaer-u-bei-lsvs-20061220, 1, en_US]
Figure 2-100
Two-Element Breaker Failure Protection
In two-element breaker failure protection, the trip command is output again to the local feeder circuit breaker,
normally to a separate set of trip coils of the feeder breaker, after the time delay TRIP-Timer (address 7005)
has elapsed.
If the circuit breaker does not respond to the repeated trip, the adjacent circuit breakers, i.e. the breakers of
the busbar or the busbar section affected, and where applicable also the breaker at the remote end, are
tripped after the time delay 50BF-2 Delay (Adresse 7008) has elapsed and the fault still exists.
The time delays to be set should be based on the maximum circuit breaker operating time plus the dropout
time of the current flow monitoring element plus a safety margin which takes into consideration the tolerance
of the time delay. In case of an external start, the set time delay is reduced automatically by 10 ms in order to
compensate the residual time of the external start.
SIPROTEC 4, 7SJ80, Manual
E50417-G1140-C343-A8, Edition 12.2017
Time sequence example for normal clearance of a fault, and for circuit breaker failure with
single-element breaker failure protection
Figure 2-100 illustrates the time sequences in an example.
Figure 2-101 illustrates the time sequences in an example.
Functions
2.17 Breaker Failure Protection 50BF
239