7SR18 Description Of Operation
Unrestricted Page 62 of 78
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Section 5: Supervision Functions
5.1
Circuit Breaker Failure (50BF)
The circuit breaker fail function has two time delayed outputs that can be used for combinations of re-tripping or
back-tripping. CB Fail outputs are given after elapse of the
50BF-1 Delay
or
50BF-2 Delay
settings. The two
timers run concurrently.
The circuit breaker fail protection time delays are initiated either from:
An output
Trip Contact
of the relay (MENU: OUTPUT CONFIG\TRIP CONFIG\Trip Contacts), or
A binary or virtual input assigned to
50BF Ext Trig
(MENU: INPUT CONFIG\INPUT MATRIX\50BF Ext
Trig).
A binary or virtual input assigned to
50BF Mech Trip
(MENU: INPUT CONFIG\INPUT MATRIX\ 50BF
Mech Trip).
CB Fail outputs will be issued providing any of the 3 phase currents are above the
50BF Setting
or the current in
the fourth CT is above
50BF-I4
for longer than the
50BF-n Delay
setting, or for a mechanical protection trip the
circuit breaker is still closed when the
50BF-n Delay
setting has expired – indicating that the fault has not been
cleared.
Both
50BF-1
and
50BF-2
can be mapped to any output contact or LED.
An output is also given to indicate the faulted phase,
50BF PhA
,
50BF PhB, 50BF PhC and 50BF EF
If the
CB Faulty
input (MENU: INPUT CONFIG\INPUT MATRIX\CB Faulty) is energised when a CB trip is given
the time delays
50BF-n Delay
will be by-passed and the output given immediately.
Operation of the CB Fail elements can be inhibited from:
Inhibit 50BF
A binary or virtual input.
Figure 5.1-1 Logic Diagram: Circuit Breaker Fail Protection (50BF)
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