2.12 Automatic Reclosure Function
127
7ST6 Manual
E50417-G1176-C251-A3
Example 2: 3 cycles are set. Initiation of the auto-reclosure is only allowed for the first.
The action times are set as in example 1. The first protection trip takes place 0.5 s after
pickup. Since the action time for the 1st cycle has already expired at this time, this
cannot start the auto reclose function. However, the 2nd and 3rd cycles cannot take
place because they are not set to initiate. There is therefore no reclosure, because no
initiating at all can take place.
Example 3: 3 cycles are set. Starting of the auto-reclosure is allowed for at least the
first two cycles. The action times are set as in example 1. The first protection trip takes
place 0.5 s after pick-up. Since the action time for the 1st cycle has already expired at
this time, it cannot start the automatic reclosure function but the 2nd cycle, for which
initiating is allowed, is activated immediately. This 2nd cycle therefore starts the auto-
matic reclosure circuit, the 1st cycle is practically skipped.
Reclosure Block
Different events lead to blocking of automatic reclosure. No reclosure is possible for
example if it is blocked via a binary input. If the automatic reclosure has not yet been
started, it cannot be started at all. If a reclosure cycle is already in progress, dynamic
blocking takes place (see below).
The first or the other cycles of the auto reclose function can also be blocked separately
via a binary input. In this case the cycle or cycles concerned will be declared as invalid,
and skipped in the sequence of permissible cycles. If blocking takes place while the
cycle concerned is already running, this leads to aborting of the reclosure, i.e. no re-
closure takes place even if other valid cycles have been parameterized.
Internal blocking states restricted to certain time periods are processed during the
course of reclosure cycles:
The reclaim time
TIME RESTRAINT
begins with every automatic reclosure command.
If the reclosure is successful, all the functions of the automatic reclosure return to the
idle state at the end of the reclaim time; a fault after expiry of the reclaim time is treated
as a new fault in the power system. If one of the protection functions causes another
trip during that period, the next reclosure cycle will be started if repeated reclosure has
been set. If no more reclosure attempts are permitted, the last reclosure is regarded
as unsuccessful in case of another trip during the blocking time. The automatic reclo-
sure is locked out dynamically.
The dynamic blocking locks the reclosure for the duration of the dynamic blocking time
(0.5 s). This occurs for example after a final tripping or other events which block the
auto reclose function after it has been started. Restarting is blocked for this time.
When this time has expired, the automatic reclosure returns to its idle position and is
ready to process a new fault in the network.
If the circuit breaker is closed manually (by the control discrepancy switch connected
to a binary input, the local control functions or via one of the serial interfaces), the auto
reclose function is blocked for a manual-close-blocking time
T-BLOCK MC
. When a
trip command is given during this time, it can be assumed that a metallic short-circuit
is present (e.g. closed earthing isolator). Every trip command within this time is there-
fore final. With the user definable logic functions (CFC) further control functions can
be processed in the same way as a manual–close command.
Interrogation of
Circuit Breaker
Ready
A precondition for automatic reclosure following clearance of a short-circuit is that the
circuit breaker is ready for at least one TRIP-CLOSE-TRIP-cycle when the automatic
reclosure circuit is started (i.e. at the time of the first trip command). The readiness of
the circuit breaker is monitored by the device using a binary input
„>CB Ready“
(FNo.
2730). If no such signal is available, the circuit breaker interrogation can be sup-
pressed (presetting) as automatic reclosure would otherwise not be possible at all.
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