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[ls-versag-zeitabl-2stuf-versag-oz-020802, 1, en_US]
Figure 2-43
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 50BF-2 Delay (address 3906) has elapsed.
The time 50BF-1 Delay 3p (address 3905) is set to ∞ 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.
currents is ≤ 15 ms. If current transformer saturation is anticipated, the time should be set to 25 ms.
[ls-versag-zeitabl-1stuf-versag-oz-020802, 1, en_US]
Figure 2-44
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 disturb-
ance (via the binary input
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
adjacent breakers (busbar trip).
SIPROTEC 4, 7SD80, Manual
E50417-G1100-C474-A2, Edition 02.2018
Time sequence example for normal clearance of a fault, and with circuit-breaker failure, using
two-element breaker failure protection
Figure 2-44
illustrates the time sequences in an example. The dropout time for sinusoidal
Time sequence example for normal clearance of a fault, and with circuit-breaker failure, using
single-element breaker failure protection
>52 faulty ), the adjacent circuit breakers (busbar and remote end if applicable)
2.6 Circuit Breaker Failure Protection 50BF
Functions
101
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