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The sequence above applies for single reclosure cycles. In 7SD5 multiple reclosure (up to 8 shots) is also pos-
sible (see below).
Multiple auto-reclosure
If a short-circuit still exists after a reclosure attempt, further reclosure attempts can be made. Up to 8 reclosure
attempts are possible with the automatic reclosure function integrated in the 7SD5.
The first four reclosure cycles are independent of each other. Each one has separate action and dead times,
can operate with 1- or 3-pole trip and can be blocked separately via binary inputs. The parameters and inter-
vention possibilities of the fourth cycle also apply to the fifth cycle and onwards.
The sequence is the same in principle as in the different reclosure programs described above. However, if the
first reclosure attempt was unsuccessful, the reclosure function is not blocked, but instead the next reclose
cycle is started. The appropriate dead time starts with the reset of the trip command or opening of the circuit
breaker (pole) (auxiliary contact criterion). The circuit breaker receives a new close command after expiry of
the dead time. At the same time the reclaim time is started.
The reclaim time is reset with each new trip command after reclosure and is started again with the next close
command until the set maximum number of permissible auto-reclose cycles has been reached.
If one of the reclosing attempts is successful, i.e. the fault disappeared after reclosure, the blocking time expires
and the automatic reclosing system is reset. The fault is cleared.
If none of the cycles is successful, the short-circuit protection initiates a final 3-pole trip after the last permissible
reclosure, following a protection stage that is valid without auto-reclosure. The automatic reclosure function is
blocked dynamically (see also margin heading „Blocking reclosure", above).
Handling Evolving Faults
When 1-pole or 1-and 3-pole reclose cycles are executed in the network, particular attention must be paid to
sequential faults.
Sequential faults are faults which occur during the dead time after clearance of the first fault.
There are various ways of handling sequential faults in the 7SD5 depending on the requirements of the net-
work:
To detect an evolving fault, you can select either the trip command of a protection function during the dead time
or every further pickup as the criterion for an evolving fault.
There are also various selectable possibilities for the response of the internal auto- reclose function to a de-
tected evolving fault.
• EV. FLT. MODE Stops AutoRecl:
The reclosure is blocked as soon as a sequential fault is detected. The tripping by the sequential fault is
always 3-pole. This applies irrespective of whether 3-pole cycles have been permitted or not. There are no
further reclosure attempts; the automatic reclosure function is blocked dynamically (see also margin heading
„Blocking reclosure", above).
• EV. FLT. MODE starts 3p AR:
As soon as a sequential fault is detected, the recloser switches to a 3-pole cycle. Each trip command is 3-
pole. The separately settable dead time for sequential faults starts with the clearance of the sequential fault;
after the dead time the circuit breaker receives a close command. The further sequence is the same as for
1- and 3-pole cycles.
The complete dead time in this case consists of the part of the dead time for the 1-pole reclosure up to the
clearance of the sequential fault plus the dead time for the sequential fault. This makes sense because the
duration of the 3-pole dead time is most important for the stability of the network.
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
2.17 Automatic Reclosure Function (optional)
Functions
325
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