Siemens siprotec 7SD5 User Manual page 302

2 Functions
wards. It is possible to set different individual parameters for the first four reclose
cycles. From the fifth cycle onwards the parameters of the fourth cycle apply.
The automatic reclosing function can be turned ON or OFF under address 3401 AUTO
RECLOSE.
A prerequisite for automatic reclosure taking place after a trip due to a short-circuit is
that the circuit breaker is ready for at least one TRIP-CLOSE-TRIP cycle at the time
the automatic reclosure circuit is started, i.e. at the time of the first trip command. The
readiness of the circuit breaker is signalled to the device through the binary input
„>CB1 Ready" (No. 371). If no such signal is available, leave the setting under
address 3402 CB? 1.TRIP = NO because no automatic reclosure would be possible
at all otherwise. If circuit breaker interrogation is possible, you should set CB? 1.TRIP
= YES.
Furthermore, the circuit breaker ready state can also be interrogated prior to every re-
closure. This is set when setting the individual reclose cycles (see below).
To check that the ready status of the circuit breaker is regained during the dead times,
you can set a circuit breaker ready monitor time under address 3409 CB TIME OUT.
The time is set slightly longer than the recovery time of the circuit breaker after a TRIP-
CLOSE-TRIP cycle. If the circuit breaker is not ready again by the time this timer ex-
pires, no reclosure takes place, the automatic reclosure function is blocked dynami-
cally.
Waiting for the circuit breaker to be ready can lead to an increase of the dead times.
Interrogation of a synchro-check (if used) can also delay reclosure. To avoid uncon-
trolled prolongation, it is possible to set a maximum prolongation of the dead time in
this case in address 3411 T-DEAD EXT.. This prolongation is unlimited if the setting
∞ is applied. This parameter can only be altered with DIGSI
tings. Remember that longer dead times are only permissible after three-pole tripping
when no stability problems arise or when a synchro-check takes place before reclo-
sure.
The blocking time T-RECLAIM (address 3403) defines the time that must elapse, after
a successful reclosing attempt, before the automatic reclosing function is reset. Re-
tripping of a protection function within this time initiates the next reclose cycle in the
event of multiple reclosure; if no further reclosure is permitted, the last reclosure is
treated as unsuccessful. The reclaim time must therefore be longer than the longest
response time of a protective function which can start the automatic reclosure circuit.
A few seconds are generally sufficient. In areas with frequent thunderstorms or
storms, a shorter blocking time may be necessary to avoid feeder lockout due to se-
quential lightning strikes or cable flashovers.
A longer reclaim time should be chosen where circuit breaker supervision is not pos-
sible (see above) during multiple reclosures, e.g. because of missing auxiliary con-
tacts and information on the circuit breaker ready status. In this case, the reclaim time
should be longer than the time required for the circuit breaker mechanism to be ready.
The blocking duration following Manual–Close–detection T-BLOCK MC (address
3404) must guarantee the circuit breaker to open and close reliably (0.5 s to 1 s). If a
fault is detected by a protection function within this time after closing of the circuit
breaker was detected, no reclosure takes place and a final three-pole trip command
is issued. If this is not desired, set address 3404 to 0.
The options for handling evolving faults are described in Section 2.15 under margin
heading „Handling Evolving Faults". The treatment of sequential faults is not neces-
sary on line ends where the adaptive dead time is applied (address 133 Auto
Reclose = ADT). The addresses 3406 and 3407 are then of no consequence and
therefore not accessible.
302
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under Additional Set-
7SD5 Manual
C53000-G1176-C169-1