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REF 610
4.1.4.8.
28
Feeder Protection Relay
Technical Reference Manual
Î L
Î 0
External Arc
Light sensor 1
OR
Light sensor 2
Fig. 4.1.4.7.-1 Block diagram of the arc protection
Auto-reclose function
The vast majority of MV overhead line faults are transient and automatically cleared
by momentarily de-energizing the line. De-energizing of the fault location for a
selected time period is implemented through automatic reclosing, during which
most faults can be cleared.
At a permanent fault, auto-reclosing is followed by definite tripping. A permanent
fault must be located and cleared before the fault location can be re-energized.
The auto-reclose (AR) function of REF 610 can be used with any circuit breaker
suitable for auto-reclosing. The AR function provides three programmable
auto-reclose shots and can thus be set to perform one to three successive
auto-reclosures of desired type and duration, one high-speed and one delayed, for
instance.
The AR function can be initiated by start and trip signals from certain overcurrent
and earth-fault protection stages. Consequently, tripping of the arc protection stage,
for instance, does not initiate the AR function. Initiation is also possible from an
external device via a digital input.
The AR function can be inhibited (AR Inhibit) by trip signals from certain
protection stages or via a digital input. Inhibition is advantageous with tripping
faults as this type of fault cannot be cleared during an auto-reclose sequence.
Tripping faults are detected by the CBFP, for instance. Inhibition will also interrupt
any ongoing shot.
The initiation of one or several auto-reclose shots can be set to be blocked by trip
signals from certain protection stages. Blocking is also possible via a digital input.
Blocking can be used to limit the number of shots in an auto-reclose sequence, which
may be advantageous with certain types of faults. In case of shot initiation while a
blocking is active, the next shot will be initiated.
The AR function monitors the position and status of the circuit breaker. Information
on the circuit-breaker position is always required whereas circuit-breaker status is
optional. For safety reasons, shot initiation is not possible when the circuit breaker
is open. If the circuit breaker is not ready, due to an discharged spring, for instance,
Arc protection
25 ms
SGF3/6=1
Arc I>
Arc I 0 >
AND
SGF4/6=0
1MRS 755310
t
Arc Trip
SGF3/7=1
L> light output
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