Functions
122
7SS52 V4 Manual
C53000-G1176-C182-3
I>query The circuit breaker failure protection (CBF) function is initiated by the TRIP command
from the feeder protection.
If the operating mode I>query is set with the parameter BF OP MODE (XX15/CU),
the feeder current is monitored for exceeding the threshold set with the parameter
I> BF (XX18/CU) or I> BF-EF (XX19/CU) (Figure 5-21, page 120).
A feeder current above this threshold starts the delay time set with the parameter T-
BF-1P (X X20/CU) or T-BF-mP (XX21/CU).
If the feeder current is still above the threshold after this delay has elapsed, the central
unit issues a 3-pole TRIP command to isolate the bus zone. In the case of a circuit
breaker failure (internal BF), the alarms "Trip Lx CZ" (FNo. 10457/CU, 10458/
CU, 10459/CU), "Trip BF G" (10436/CU), "Device trip G" (FNo. 10445/
CU) "Fault rec. run." (FNo. 30053/CU), "Trip BF $03 Lx"
(177.1352.$03/CU, 177.1353.$03/CU, 177.1354.$03/CU), "Trip $03 G"
(177.1341.$03/CU), "Trip Lx G" (FNo. 10446/CU, 10447/CU, 10448/CU),
"TrnsfTrip $00" (176.1082.$00/CU) and the group alarm "Transf. Trip G"
(10433/CU) will be issued.
trip rep/I>quer If the operating mode trip rep/I>quer is set with the parameter BF OP MODE
(XX15/CU), the current is monitored for exceeding the threshold set with the parame-
ter I> BF (XX18/CU) or I> BF-EF (XX19/CU). A current above this threshold starts
the delay time for the TRIP repetition, which is set with the parameter T-TRIP re-
pea
t (XX25/CU).
If this release criterion is fulfilled for all of the delay time for the TRIP repetition, the
bay unit issues a 1-pole or 3-pole TRIP command to the local circuit breaker.
A single-pole TRIP repetition is generated on condition that the feeder current in the
CBF-initiating phase and at least one of the other currents (phase or ground current)
exceed the adjustable threshold (ILx & IE) set with the parameter I> BF (XX18/CU)
or I> BF-EF (XX19/CU). For this purpose, set the parameter TRIP REP. MODE
(XX17/CU) to 1pole. The TRIP repetition is always three-polar if the feeder current
exceeds in at least 2 phases the value set with the parameters I> BF (XX18/CU) or
I> BF-EF (XX19/CU).
If the circuit breaker trips correctly, the initiation and thus the CBF function is cleared.
If the CBF initiation persists, the time delay of the CBF - set with the parameter T-BF-
1P (XX20/CU) or T-BF-mP (XX21/CU) - elapses. In conformity with the current isola-
tor replica, all feeders are tripped which are allocated to the bus zone of the CBF ini-
tiating bay unit.
A further condition is that the current threshold, which can be set individually for each
feeder with the parameter I> BF (XX18/CU), is exceeded during the total time period.
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