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3-70
Protection Functions
Circuit-breaker failure
protection CBFP (50BF)
857-UM001A-EN-P – July 2009
The circuit breaker failure protection can be used to trip any upstream
circuit breaker (CB), if the fault has not disappeared within a given
time after the initial trip command. A different output contact of the
relay must be used for this backup trip.
The operation of the circuit-breaker failure protection (CBFP) is
based on the supervision of the signal to the selected trip relay and
the time the fault remains on after the trip command.
If this time is longer than the operating time of the CBFP stage, the
CBFP stage activates another output relay, which will remain
activated until the primary trip relay resets.
The CBFP stage is supervising all the protection stages using the
same selected trip relay, since it supervises the control signal of this
relay. See "Output Matrix" in Chapter 6 for details about the output
matrix and the trip relays.
Table 3.42 – Parameters of the Circuit Breaker Failure Stage CBFP (50BF)
Parameter
Value
Status
-
Blocked
Start
Trip
SCntr
TCntr
Force
Off
On
CBrelay
1 - 14
t>
For details of setting ranges see "Protection Stages" in Chapter 10.
Set = An editable parameter (password needed)
C = Can be cleared to zero
F = Editable when force flag is on
This setting is also used by the circuit breaker condition monitoring. See "Circuit Breaker
Condition Monitoring" in Chapter 4.
Unit
Description
Current status of the stage
Cumulative start counter
Cumulative trip counter
Force flag for status forcing for test
purposes. This is a common flag
for all stages and output relays, too.
Automatically reset by a 5-minute
timeout.
The supervised output relay
Relay T1 – T14 (depending on the
orderinf code)
s
Definite operation time
Note
F
F
C
C
Set
Set
Set
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