Functions
2.6 Circuit-Breaker Failure Protection 50BF
SIPROTEC, 7SD80, Manual
E50417-G1140-C474-A1, Release date 09.2011
110
Malfunction of the Local Circuit Breaker
If the circuit breaker associated with the feeder is not operational (e.g. control voltage failure or air pressure
failure), it is apparent that the local breaker cannot clear the fault. If the relay is informed about this disturbance
(via the binary input „>52 faulty“), the adjacent circuit breakers (busbar and remote end if applicable) are
tripped after the time T3-BkrDefective (address 3907) which is usually set to 0.
Address 3908 Trip BkrDefect. determines to which output the trip command is routed in the event that the
breaker is not operational when a feeder protection trip occurs. Select that output which is used to trip the ad-
jacent breakers (busbar trip).
End Fault Protection
The end fault protection can be switched separately ON or OFF in address 3921 End Flt. elem.. An end
fault is a fault between the circuit breaker and the current transformer set of the feeder. The end fault protection
presumes that the device is informed about the circuit-breaker position via breaker auxiliary contacts connected
to binary inputs.
If, during an end fault, the circuit breaker is tripped by a reverse element of the feeder protection or by the
busbar protection (the fault is a busbar fault as determined from the location of the current transformers), the
fault current will continue to flow, because the fault is fed from the remote end of the feeder circuit.
The time EndFault Delay (address 3922) is started when, during the time of pickup condition of the feeder
protection, the circuit-breaker auxiliary contacts indicate open poles and, at the same time, current flow is still
detected (address 3902). The trip command of the end fault protection is intended for the transmission of an
intertrip signal to the remote end circuit breaker.
Thus, the time delay must be set such that it can bridge out short transient apparent end fault conditions which
may occur during switching of the breaker.
2.6.3 Settings
The table indicates region-specific default settings. Column C (configuration) indicates the corresponding sec-
ondary nominal current of the current transformer.
Addr. Parameter C Setting Options Default Setting Comments
3901 FCT 50BF Break. ON
OFF
ON 50BF Breaker Failure Pro-
tection
3902 50BF PICKUP 1A 0.05 .. 20.00 A 0.10 A 50BF Pickup current
threshold
5A 0.25 .. 100.00 A 0.50 A
3905 50BF-1 Delay 3p 0.00 .. 30.00 sec; ∞ 0.00 sec Delay after 3pole start for
local trip
3906 50BF-2 Delay 0.00 .. 30.00 sec; ∞ 0.15 sec Delay of 2nd element for
busbar trip
3907 T3-BkrDefective 0.00 .. 30.00 sec; ∞ 0.00 sec Delay for start with defec-
tive bkr.
3908 Trip BkrDefect. NO
with Local trip
with Bus trip
w/Local&Bustrip
NO Trip output selection with
defective bkr
3909 Chk BRK CONTACT NO
YES
YES Check Breaker contacts
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