Siemens 7SC80 Manual page 279

Restraint Time and Dynamic Blocking
The blocking time TIME RESTRAINT(address 7105) defines the time that must elapse, after a successful
reclosing attempt, before the automatic reclosing function is reset. If a protective function configured for
initiation of the automatic reclosure function provokes a new trip before this time elapses, the next reclosing
cycle is started in case of multiple reclosures. If no further reclosure is allowed, the last reclosure will be
classed as unsuccessful.
In general, a few seconds are sufficient. In areas with frequent thunderstorms or storms, a shorter blocking
time may be necessary to avoid feeder lockout due to sequential lightning strikes or flashovers.
A longer restraint time should be chosen if there is no possibility to monitor the circuit breaker (see below)
during multiple reclosing (e.g. because of missing auxiliary contacts and information on the circuit breaker
ready status). In this case, the restraint time should be longer than the time required for the circuit breaker
mechanism to be ready.
If a dynamic blocking of the automatic reclosing function was initiated, then reclosing functions remain
blocked until the cause of the blocking has been cleared. The functional description gives further information
on this topic, see side title "Dynamic Blocking". The dynamic blocking is associated with the configurable
blocking time SAFETY 79 ready. Blocking time is usually started by a blocking condition that has picked up.
Circuit Breaker Monitoring
Reclosing after a fault clearance presupposes that the circuit breaker is ready for at least one TRIP-CLOSETRIP
cycle at the time when the reclosing function is initiated (i.e. at the beginning of a trip command):
The readiness of the circuit breaker is monitored by the device using a binary input
•
It is possible to check the status of the circuit breaker before each reclosure or to disable this option
(address 7113, CHECK CB?):
CHECK CB? = No check, deactivates the circuit breaker check,
CHECK CB? = Chk each cycle, to verify the circuit breaker status before each reclosing command.
Checking the status of the circuit breaker is usually recommended. Should the breaker not provide such a
signal, you can disable the circuit breaker check at address 7113 CHECK CB? (No check), as otherwise
auto-reclosure would be impossible.
The status monitoring time CB TIME OUT can be configured at address 7115 if the circuit breaker check
was enabled at address 7113. This time is set slightly higher than the maximum recovery time of the
circuit breaker following reclosure. If the circuit breaker is not ready after the time has expired, reclosing
is omitted and dynamic blocking is initiated. Automatic reclosure thus is blocked.
The time Max. DEAD EXT. at address 7116 serves to monitor the dead time extension. The extension can be
initiated by the circuit breaker monitoring time CB TIME OUT, address 7115.
The monitoring time Max. DEAD EXT. is started after the configured dead time has elapsed.
This time must not be shorter than the monitoring time CB TIME OUT. When using the monitoring time CB
TIME OUT, the time Max. DEAD EXT. should be set to a value ≥ CB TIME OUT.
The breaker failure monitoring time 7114 T-Start MONITOR determines the time between tripping (closing
the trip contact) and opening the circuit breaker (checkback of the CB auxiliary contacts or disappearing device
pickup if no auxiliary contacts are allocated). This time is started each time a tripping operation takes place.
When time has elapsed, the device assumes breaker failure and blocks the automatic reclosure function
dynamically.
Action Time
The action time monitors the time between pickup of the device and trip command of a protective function
configured as starter while the automatic reclosure function is ready but not yet running. A trip command
issued by a protective function configured as starter occurring within the action time will start the automatic
reclosing function. If this time differs from the setting value of T-ACTION (address 7117), the automatic
reclosure function will be blocked dynamically. The trip time of inverse tripping characteristics is considerably
determined by the fault location or fault resistance. The action time prevents reclosing in case of far remote or
high-resistance faults with long tripping time. Trip commands of protective functions which are not config-
ured as starter do not affect the action time.
SIPROTEC Compact, 7SC80, Manual
E50417-G1140-C486-A8, Edition 07.2017
Functions
2.14 Automatic Reclosing System 79
>CB Ready (FNo. 2730).
279