Technical description
2 Protection functions
2.10 Circuit-breaker failure
protection CBFP (50BF)
VM265.EN011
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Measured and recorded values of second harmonic
blocking 2.Ha(51F2):
Parameter Value
Unit
Description
Measured
values
IL1H2.
%
2. harmonic of IL1,
proportional to the
fundamental value of
IL1
IL2H2.
%
2. harmonic of IL2
IL3H2.
%
2. harmonic of IL3
Recorded
values
Flt
%
The max. fault value
EDly
%
Elapsed time as
compared to the set
operating time; 100%
= tripping
2.10.
Circuit-breaker failure protection CBFP
(50BF)
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 chapter 5.4 for details about the output
matrix and the trip relays.
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