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REF 610
4.1.4.5.
4.1.4.6.
4.1.4.7.
26
Feeder Protection Relay
Technical Reference Manual
Phase discontinuity protection
The phase discontinuity protection detects phase unbalance between phases I
and I
, caused by a broken conductor, for instance. The difference between the
L3
minimum and maximum phase currents is calculated as follows:
(
)
Imax Imin
–
∆I
-----------------------------------
=
Imax
When the current difference exceeds the set start value of the phase discontinuity
stage, ∆I>, the stage will generate a start signal after a ~ 100 ms' start time. When
the set operate time at definite-time characteristic elapses, the stage will generate a
trip signal. The stage will be reset in 70 ms after the current difference has fallen
below the set start value of the stage.
The phase discontinuity protection will be inhibited when all phase currents fall
below 0.1 x I
.
n
It is possible to block the tripping of the phase discontinuity stage by applying a
digital input signal to the relay.
Stage ∆I> can be set out of operation in SGF3. This state will be indicated by dashes
on the LCD and by "999" when the set start value is read via serial communication.
Circuit-breaker failure protection
The circuit-breaker failure protection (CBFP) 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 CBFP set operate time, the CBFP will generate a trip
signal via output PO2.
Note!
The CBFP will not be triggered in case of a thermal alarm, thermal or external trip.
The CBFP can also be selected to be triggered by applying a digital input signal to
the relay. In this case, the CBFP will generate a trip signal via output PO2 if the
current has not been cut off on expiration of the set operate time.
Internal triggering is selected by activating the CBFP in SGF and external triggering
by activating the CBFP in SGB. Both triggering options can be selected at the same
time.
Normally, the CBFP controls the upstream circuit breaker. However, it can also be
used for tripping via redundant trip circuits of the same circuit breaker.
Arc protection
The arc protection detects arc situations in air insulated metal-clad switchgears,
caused by human error during maintenance or poor contact in the cable connections,
for instance. Local light detection requires the optional arc light detection hardware.
The arc protection can be realized as a stand-alone function in a single REF 610 or
as a station-wide arc protection including several REF 610 protection relays. If
realized as a station-wide arc protection, different tripping schemes can be selected
×
100%
1MRS 755310
, I
L1
L2
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