Page 5-37
IL17569
Effective June, 2001
5.5.2.7 Breaker Failure
50BF Bkr Config
This is the 50BF device Breaker Failure Configuration setting. The
50BF Bkr Config sets the conditions for the FP-5000 to detect a
breaker failure condition. This function is only activated after initiation.
The four 50BF Bkr Config setting descriptions are shown below:
50BF Bkr Config The 50BF device is turned off, so no
set to Off: breaker failure can be detected
internally or externally.
50BF Bkr Config The 50BF function will be initiated by
set to Internal: an internal trip signal.
50BF Bkr Config The 50BF function will be initiated by
set to External: an external signal.
50BF Bkr Config The 50BF function will be initiated by
set to Both: either an internal or external trip
signal.
50BF Bkr Failure: This includes the 50BF device
Breaker Failure setting, which is only
applied if the 50BF Bkr Config setting
is not set to “off.” The default
configuration for the output logic
maps the Breaker Failure trip (i.e.
Breaker State Lockout) to output
Relay 3 so that a separate lockout
relay (device 86) can be used to
provide backup tripping. The breaker
failure function continues to monitor
all phase currents after a trip is
initiated by ether the FP-5000 or an
external device. The breaker failure
trip output operates if the phase or
ground currents do not drop below the
programmed I Ph (pu) or I Gnd (pu)
setting levels within the breaker
failure Delay time setting.
Figure 5-2. Breaker Failure Logic Diagram
The I Ph (pu) is an independent overcurrent
element monitoring the phase currents. It is
recommended to set the level above maximum
load currents even though the Breaker failure
logic is only initiated upon a breaker trip signal.
The I Gnd (pu) is an independent ground
overcurrent element that uses both the
measured residual ground current (Ir) and the
measured ground current (Ix). It is recom-
mended to be set above any normal or
expected rms ground currents.
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