Siemens SIPROTEC 7SD610 Manual page 131

(adjustable) reclaim time is started. If the reclosure is blocked during the dead time following a 1-pole trip, im-
mediate 3-pole tripping can take place as an option (forced 3-pole trip).
If the fault is cleared (successful reclosure), the reclaim time expires and all functions return to their quiescent
state. The fault is cleared.
If the fault has not been eliminated (unsuccessful reclosure), the short-circuit protection initiates a final 3-pole
trip with the protection stage that is valid without reclosure. All faults during the reclaim time also lead to a final
3-pole trip.
After unsuccessful reclosure (final tripping), the automatic reclosure function is blocked dynamically (see also
margin heading „Reclose Block", above).
The sequence above applies for single reclosure cycles. In 7SD610 multiple reclosure (up to 8 shots) is also
possible (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 7SD610.
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.
Evolving 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 7SD610 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.
SIPROTEC, 7SD610, Manual
C53000-G1176-C145-6, Release date 02.2011
2.10 Automatic Reclosure Function (optional)
Functions
131