Siemens 7SC80 Manual page 272

Functions
2.14 Automatic Reclosing System 79
Reclosing Before Selectivity
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 has thus priority over selectivity
aspects as the reclosing action aims at maintaining normal system operation. For this purpose, all protection
functions which can initiate the automatic reclosure function are set in such manner that they may trip instan-
taneously or with a very small time delay before automatic reclosure.
With final closing, however, that is if no automatic reclosing can be expected, the protection is to trip with
delay according to the grading coordination chart of the system, since selectivity has the priority in this case.
See also the information under the margin heading "Interaction with the Automatic Reclosing Function" in the
Setting Notes of the time overcurrent protection functions.
Single-Shot Reclosing
When a trip signal is programmed to initiate the automatic reclosure, the appropriate 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 func-
tion is dynamically blocked causing the final tripping of the circuit breaker. The dead time can be set individu-
ally 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 configured.
If the fault is cleared (successful reclosing attempt), the blocking time expires and automatic reclosing is reset
in anticipation of a future fault. The fault is terminated.
If the fault has not been cleared (unsuccessful reclosing attempt), then a final trip signal is initiated by one or
more protective elements.
Multi-shot Reclosing
7SC80 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 preceding the first four reclosing attempts can be set differently for each of the two
reclosing programs. The dead time intervals preceding the fifth reclosing attempts will be equal to the dead
time interval that precedes the fourth reclosing attempt.
If one of the reclosing attempts is successful, i.e. the fault disappeared after reclosure, the restraint time
expires and the automatic reclosing function is reset. The fault is cleared.
If none of the reclosing attempts is successful, then a final circuit breaker trip (according to the grading coordi-
nation chart) will take place after the last allowable reclosing attempt has been performed by the protection
function. All reclosing attempts were unsuccessful.
After the final circuit breaker tripping, the automatic reclosing function is dynamically blocked (see below).
Blocking Time
The function of the blocking time has already been described under section "Single-/Multi-Shot Reclosing". The
blocking time can be prolonged if the following conditions have been fulfilled.
The time 211 TMax CLOSE CMD defines the maximum time during which a close command can apply. If a
new trip command occurs before this time has run out, the close command will be canceled. If the time TMax
CLOSE CMD is set longer than the restraint time TIME RESTRAINT, the restraint time will be extended to the
remaining close command duration after expiry!
A pickup from a protection function that is set to initiate the automatic reclosing function will also lead to an
extension of the blocking time should it occur during this time!
272 SIPROTEC Compact, 7SC80, Manual
E50417-G1140-C486-A8, Edition 07.2017