Phase Discontinuity Protection; Circuit-Breaker Failure Protection - ABB REF610 Technical Reference Manual

REF610 REF610
5.1.4.5.
5.1.4.6.
36
Feeder Protection Relay
Technical Reference Manual - ANSI Version

Phase discontinuity protection

The phase discontinuity protection detects phase unbalance between phases Ia, Ib
and Ic, caused by a broken conductor, for instance. The difference between the
minimum and maximum phase currents is calculated as follows:
−
I I
( )
= ×
max min
I unbal 100
I
max
When the current difference exceeds the set pickup value of the phase discontinuity
element, 46, the element will generate a pickup signal after a ~100 ms' pickup time.
When the set operate time at definite-time characteristic elapses, the element will
generate a trip signal. The element will be reset in 70 ms after the current difference
has fallen below the set pickup value of the element.
The phase discontinuity protection will be disabled when all phase currents fall
below 0.1 x CT.
It is possible to block the tripping of the phase discontinuity element by applying a
digital input signal to the relay.
Element 46 can be set out of operation in SGF3. This state will be indicated by
dashes on the LCD and by "999" when the set pickup value is read via serial
communication.

Circuit-breaker failure protection

The circuit-breaker failure protection (CBFAIL) detects situations where the trip
remains active although the circuit breaker should have operated.
If a trip signal generated via output PO1 is still active and the current has not been
cut off on expiration of the CBFAIL set operate time, the CBFAIL generates a trip
signal via output PO2.
The CBFAIL is not triggered in case of:
Thermal alarm
*
Thermal trip
*
External trip
*
The CBFAIL can also be selected to be triggered externally by applying a digital
input signal to the relay. In this case, the CBFAIL generates a trip signal via output
PO2 if the current has not been cut off on expiration of the set operate time.
External triggering is disabled when all phase currents fall below 12 percent of the
rated current, I (CT).
n
Internal triggering is selected by activating the CBFAIL in SGF and external
triggering by activating the CBFAIL in SGB. Both triggering options can be
selected at the same time.
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1MRS755535
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