ABB SPAC 531 C User Manual And Technical Description page 29

The final CB trip signal delivered by the over-
current and earth-fault relay module (contacts
X1/6-7 or X2/1-2-3) is delayed about 40 ms by
the electronics of the relay. When the AR func-
tions are initiated by starting of the phase over-
current module, the starting time setting of the
auto-reclose unit must be 50 ms shorter than the
operate time t> of the phase overcurrent module
to prevent the signal contact X1/6-7 from pro-
viding an unwanted signal when an auto-reclose
sequence starts. After that the operation of the
signalling relay is blocked when an auto-reclose
sequence starts. This situation is illustrated in
Fig 13 a.
When the neutral overcurrent module starts an
auto-reclose sequence, the starting time setting
of the auto-reclose unit should be about 150 ms
shorter than the operate time t> of the neutral
overcurrent module.
In the situation above there is enough time for
the red operation indicator of the phase overcur-
rent and neutral overcurrent module to go on
and information about tripping is received over
the SPA bus, although no contact alarm signal is
received. To prevent the red operation indica-
tor from going on and the trip message from
being transmitted over the serial bus, the start-
ing time setting of the auto-reclose unit should
be about 100 ms + CB operate time t
than the operate time t> of the phase overcur-
rent module. Fig. 13 b illustrates this situation.
In the same way the starting time setting of the
auto-reclose unit has to be about 200 ms + CB
operating time t shorter than the operate time
cb
of the earth-fault relay module.
The starting times of the auto-reclose unit can
also be used for time grading functions when the
feeder includes line branch circuit breakers.
Starting of the auto-reclose functions regarding
the entire feeder can be delayed so much that the
branch circuit breaker relay has time to operate
and open the circuit breaker of the faulty branch.
By grading the operate times of the relays of the
branch circuit breakers it is possible to locate a
faulty branch on the basis of the durations of the
starting signals recorded by the substation re-
lays.
The auto-reclose function of the control mod-
ule allows five successive HSAR and/or DAR
cycles. The dead time of each auto-reclose cycle
can be set in the range 0.2...300 s, at 0.1 s steps.
When voltage controlled line sectionalizers are
used, this feature can be used for locating a fault.
The first isolator opens during the first AR cycle,
the second during the second AR cycle and so
on. Should the fault persist after the last DAR,
final CB tripping will follow.
The AR counters of the control module provide
specific information about the cause of an auto-
reclose function. The information of these
counters, data recorded by the measuring mod-
ules and statistical information indicate what
measures are to be taken, that is, if it is necessary
to clear a line road or to remove snow from the
line or if there is a normal earth fault or short
circuit caused by atmospheric overvoltages. The
counter data also show whether a connection
inrush current has caused unwanted DAR func-
tions.
When the circuit breaker is closed manually
over the control module, either locally or re-
motely, the reclaim time starts and the auto-
reclose functions are blocked. Before the auto-
reclose program opens or closes the circuit
breaker, it checks the blocking program, to find
shorter out whether the control operation is permitted
cb
or not.
When the circuit breaker is closed manually, but
not via the push-buttons of the control module
or via the remote control system, the connection
inrush current may lead to an unwanted auto-
reclose function. This can be avoided by apply-
ing a blocking signal to the auto-reclose unit
when the CB is closed and by giving the input
the function of blocking and interrupting auto-
reclose functions. The blocking signal is routed
to terminals X4/6-7 of the feeder terminal.
When the circuit breaker is closed against a fault
this blocking signal provides final CB tripping
without auto-reclosures. The blocking signal
can also be used for interrupting an auto-reclose
sequence going on.
The auto-reclose functions can be tested by
means of the Trip test function of the relay
modules. This test includes the entire auto-
reclose sequence plus the circuit breaker.
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