Siemens SIPROTEC 7UT613 series Manual page 271

Figure 2-109 Logic diagram of the breaker failure protection (simplified)
7UT613/63x Manual
C53000-G1176-C160-2
After initiation the timer T2 is started. When this time has elapsed, the indication „BF
T2-TRIP(bus)" (Fno 047.2655) appears which is also intended for trip of the adja-
cent breakers.
With two-stage breaker failure protection the trip command of the initiating protection
is repeated in a first stage of the breaker failure protection T1 on the feeder circuit
breaker, usually on a second trip coil. This is achieved via the output indication „BF
T1-TRIP(loc)" (Fno 047.2654). A second time stage T2 monitors the response to
this repeated trip command and is used to trip the adjacent breakers of the busbar or
busbar section if the fault has not yet been cleared after the repeated trip command.
The output indication „BF T2-TRIP(bus)" (Fno 047.2655) is again used for tripping
the adjacent breakers.
Indication numbers and indication designations refer tot he first circuit-breaker failure
protection.
2.17 Circuit Breaker Failure Protection
271