ABB REF 610 Technical Reference Manual page 29

1MRS 755535
Feeder Protection Relay
Technical Reference Manual - ANSI Version
The initiation of one or several auto-reclose shots can be set to be blocked by trip
signals from certain protection elements. 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,
reclosing can be disabled via a digital input (CB Close Disable). Disable of
reclosing is checked only when necessary and can therefore not be used to prevent
initiation or progression of a shot.
For co-ordination of the other protection devices in the network, such as
down-stream fuses, the AR function supports optional blocking of selectable
overcurrent and ground-fault protection elements (refer to section Blocking of
protection elements). By setting a element with a short operate time to trip and
initiate only the first auto-reclose shot, fast tripping and shot initiation will be
achieved. After this, the element will be blocked to allow selective delayed tripping
of another element in accordance with the time-grading plan of the system.
The typical auto-reclose sequence is as follows: the overcurrent or ground-fault
protection detects a network fault, trips the circuit breaker and initiates the first
auto-reclose shot. At the time of shot initiation, the set open time for shot 1 will
pickup. When the set open time elapses, the blocking of selected protection elements
will be activated and the AR function will issue a reclosing command (Close CB
Command) to the circuit breaker, the duration of which is settable. In addition, the
set reset time and set cutout time will pickup when the set open time elapses. The
blocking of protection elements will be reset on expiration of the cutout time. For
the cutout time, refer to section Fast tripping and initiation of shot 1 using two
protection elements.
If the network fault is cleared, i.e. the auto-reclosure is successful, the set reset time
will expire and the AR function will be automatically reset to the quiescent
condition.
However, if the network fault is not cleared, i.e. the auto-reclosure is unsuccessful,
and the protection trips the circuit breaker before expiration of the set reset time, the
next shot will be initiated (provided that a further auto-reclosure is allowed). At the
time of shot initiation, the set open time for shot 2 will pickup. When the set open
time elapses, the blocking of selected protection elements (may differ from shot 1)
will be activated and the AR function will issue a reclosing command to the circuit
breaker. In addition, the set reset time and set cutout time will pickup when the set
open time elapses. The blocking of protection elements will be reset on expiration
of the set cutout time.
If the network fault is cleared, the AR function will be automatically reset after the
reset time. However, if the fault is not cleared and the protection trips the circuit
breaker before expiration of the reset time, the next shot will be initiated (provided
that a further auto-reclosure is allowed). At the time of shot initiation, the set open
time for shot 3 will pickup. When the set open time elapses, the blocking of selected
protection elements (the same as for shot 2) will be activated and the AR function
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