Siemens siprotec SJ62 User Manual page 234

Reclosing Before
Selectivity
Single-shot Reclos-
ing
Multi-shot Reclos-
ing
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015
For the automatic reclosure sequence to be successful, faults on any part of the line
must be cleared from the feeding line end(s) within the same – shortest possible –
time. Usually, therefore, an instantaneous protection element is set to operate before
an automatic reclosure. Fast fault termination thus has priority over selectivity aspects
as the reclosing action aims at maintaining normal system operation. For this purpose
all protective functions which can initiate the automatic reclosure function are set such
that they may trip instantaneously or with a very small time delay before auto-reclo-
sure.
With the final reclosing attempt, i.e. when no automatic reclosure is expected, protec-
tion is to trip with delay according to the grading coordination chart of the network,
since selectivity has priority. For details see also information at margin heading "Using
the Automatic Reclosure Function" which can be found with the setting notes of the
time overcurrent protection functions and the functional description of the intermittent
ground fault protection.
When a trip signal is programmed to initiate the automatic reclosing system, the ap-
propriate automatic reclosing program will be executed. Once the circuit breaker has
opened, a dead time interval in accordance with the type of fault is started (see also
margin heading "Reclosing Programs"). Once the dead time interval has elapsed, a
closing signal is issued to reclose the circuit breaker. A blocking time interval TIME
RESTRAINT is started at the same time. Within this restraint time it is checked whether
the automatic reclosure was performed successfully. If a new fault occurs before the
restraint time elapses, the automatic reclosing system is dynamically blocked causing
the final tripping of the circuit breaker. The dead time can be set individually for each
of the two reclosing programs.
Criteria for opening the circuit breaker may either be the auxiliary contacts of the circuit
breaker or the dropout of the general device pickup if auxiliary contacts are not con-
figured.
If the fault is cleared (successful reclosing attempt), the blocking time expires and au-
tomatic reclosing is reset in anticipation of a future fault. The fault is cleared.
If the fault is not cleared (unsuccessful reclosing attempt), then a final tripping signal
is initiated by one or more protective elements.
7SJ62/63/64 permits up to 9 reclosings. The number can be set differently for the
phase fault reclosing program and the ground fault reclosing program.
The first reclose cycle is, in principle, the same as the single-shot auto-reclosing. If the
first reclosing attempt is unsuccessful, this does not result in a final trip, but in a reset
of the restraint time interval and start of the next reclose cycle with the next dead time.
This can be repeated until the set number of reclosing attempts for the corresponding
reclose program has been reached.
The dead time intervals for the first four reclosing attempts can be set differently for
each of the two reclosing programs. The dead time intervals from the fifth cycle on will
be equal to that of the fourth cycle.
If one of the reclosing attempts is successful, i.e. the fault disappeared after reclosure,
the restraint time expires and the automatic reclosing system is reset. The fault is ter-
minated.
If none of the reclosing attempts is successful, then a final circuit breaker trip (accord-
ing to the grading coordination chart) will take place after the last allowable reclosing
attempt has been performed by the protection function. All reclosing attempts were un-
successful
2.14 Automatic Reclosing System 79
232