Siemens SIPROTEC 7SA522 Manual page 235

Handling Evolving
Faults
7SA522 Manual
C53000-G1176-C155-3
via binary inputs. The parameters and intervention 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) (aux-
iliary 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.
Until the set maximum number of permissible auto-reclose cycles has been reached,
the reclaim time is reset with every new trip command after reclosure and started
again with the next close command.
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 three-pole
trip after the last permissible reclosure, following a protection stage active without
auto-reclosure. The automatic reclosure is blocked dynamically (see also margin
heading "Reclose Block", above).
When single-pole and single and three-pole reclose cycles are executed in the net-
work, 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 7SA522 depending on the
requirements of the network:
For the Detection of an evolving fault you can select whether the trip command of a
protective function during the dead time or every further pickup is the criterion for an
evolving fault.
There are also various selectable possibilities for the response of the internal auto-
reclose function to a detected evolving fault.
• (9 )/7 02'( EORFNV $5:
The reclosure is blocked as soon as an evolving fault is detected. Tripping as a
result of the sequential fault is three-pole. This applies irrespective of whether three-
pole cycles are permitted or not. There are no further reclosure attempts; the auto-
reclosure is blocked dynamically (see also margin heading "Reclose Block",
above).
• (9 )/7 02'( VWDUWV S $5:
As soon as a sequential fault is detected the recloser switches over to a three-pole
reclose cycle. All trip commands are now three-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 single and three-pole cycles.
The complete dead time in this case consists of the portion of the single pole dead
time up to clearance of the sequential fault plus the dead time for the sequential
fault. This makes sense because the duration of the three-pole dead time is most
important for the stability of the network.
If reclosure is blocked due to a sequential fault without the protection issuing a three-
pole trip command (e.g. for sequential fault detection with starting), the device can
2.13 Automatic reclosure function (optional)
235