2 Functions
124
7SD610 Manual
C53000-G1176-C145-4
This is the usual case in differential protection schemes because the strict selective
zone definition of the protected object by the current transformer sets always allows
non-delayed tripping.
However, fast tripping of the protection may also be desired before reclosure after trip-
ping by other short-circuit protection functions. For this purpose, every short-circuit
protection which can start the automatic reclosure function has the possibility of initi-
ating non-delayed tripping in at least one stage when the automatic reclosure function
is ready for the first reclosure cycle. Please note, however, that fast, non-selective trip-
ping should be avoided as long as the differential protection works properly: there
should be no non-delayed tripping of the overcurrent time protection as the backup
protection function, even if there is an automatic reclosure.
Fast tripping before reclosure is also possible with multiple reclosures. Appropriate
links between the output signals (e.g. 2nd reclosure ready: „AR 2.CycZoneRel“)
and the inputs for enabling/releasing non-delayed tripping of the protection functions
can be established via the binary inputs and outputs or the integrated user-definable
logic functions (CFC).
Initiation Initiation of the automatic reclosure means storing the first trip signal of a power
system fault that was generated by a protection function which operates with the au-
tomatic reclosure function. In case of multiple reclosure, initiation therefore only takes
place once, with the first trip command. This storing of the first trip signal is the pre-
requisite for all subsequent activities of the automatic reclosure function. The starting
is important when the first trip command has not appeared before expiry of an action
time (see below under „Action times“).
Automatic reclosure is not started if the circuit breaker has not been ready for at least
one OPEN-CLOSE-OPEN–cycle at the instant of the first trip command. This can be
achieved by setting parameters. For further information, please refer to „Interrogation
of Circuit Breaker Ready State“.
Each short-circuit protection function can be parameterized as to whether it should
operate with the automatic reclose function or not, i.e. whether it should start the
reclose function or not. The same goes for external trip commands applied via binary
input and/or the trip commands generated by the teleprotection via permissive or in-
tertrip signals.
Those protection and monitoring functions in the device which do not respond to short-
circuits or similar conditions (e.g. an overload protection) do not initiate the automatic
reclosure function because a reclosure will be of no use here. The breaker failure pro-
tection must not start the auto-reclosure either.
Action Times It is often desirable to remove the ready-for-reclosure-state if the short-circuit condition
was sustained for a certain time, e.g. because it is assumed that the arc has burned
in to such an extent that there is no longer any chance of automatic arc extinction
during the reclose dead time. Also for reasons of selectivity (see above), faults that are
usually cleared after a time delay should not lead to reclosure.
The automatic reclosure function of the 7SD610 can be operated with or without action
times (configuration parameter AR control mode, address 134, see Section
2.1.1.2). No starting signal is necessary from the protection functions or external pro-
tection devices that operate without action time. Initiation takes place as soon as the
first trip command appears.
When operating with action time, an action time is available for each reclose cycle.
The action times are always started by the general starting signal (with logic OR com-
bination of all internal and external protection functions which can start the automatic
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