Functions
206
7SS52 V4 Manual
C53000-G1176-C182-3
5.18.2 Setting Notes
BackUp CBF The parameter BackUp CBF (3901/BU) is used to activate and deactivate the break-
er failure protection of the bay unit.
B.U.CBF-I The parameter B.U.CBF-I (3911/BU) is used to set the current threshold for the
breaker failure protection of the bay unit. In the case of a circuit breaker malfunction,
the TRIP repetition of the backup breaker failure protection is zero.
When setting this parameter, you should also consider the corresponding parameter
of the breaker failure protection in the central unit, so that the two protection functions
complement each other in a meaningful way. Siemens therefore recommends to
match the value in the bay unit to its counterpart in the central unit.
B.U.CBF-T Use parameter B.U.CBF-T (3912/BU) to set the time delay for the feeder-selective
TRIP command (TRIP repetition) of the backup breaker failure protection of the bay
unit. In the case of a circuit breaker fault the TRIP repetition time delay of the backup
CBF is zero. The two time delays for TRIP repetition and CBF trip command start one
after the other.
When setting this parameter, you should also consider the corresponding parameter
of the breaker failure protection in the central unit, so that the two protection functions
complement each other in a meaningful way. Siemens therefore recommends to
match the value in the bay unit to its counterpart in the central unit.
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