Siemens SIPROTEC 4 7VK61 Manual Download

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Initiation

Initiation of the automatic reclosure function means storing the first trip signal of a power system fault that
was generated by a protection function which operates with the automatic 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 prerequisite 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 function 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 auto-
matic 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 intertrip 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 circuit breaker failure protection must not start the automatic reclosure function
either.

Action Times

It is often desirable to neutralise 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 the sake of selectivity (see
above), faults that are usually cleared after a time delay should not lead to reclosure.
The automatic reclosure function of the 7VK61 can be operated with or without action times (configuration
parameter

AR control mode

, address 134). No starting signal is necessary from the protection functions or

external protection 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 combination of all internal and external protection
functions which can start the automatic reclose function). If no trip command is present before the action
time expires, the corresponding reclosure cycle is not carried out.
For each reclosure cycle, it can be specified whether or not it should allow the initiation. Following the first
general pickup, only those action times are relevant whose cycles allow starting because the other cycles are
not allowed to initiate. By means of the action times and the permission to start the recloser (permission to be
the first cycle that is executed), it is possible to determine which reclose cycles are executed depending on the
time it takes the protection function to trip.
Example 1: 3 cycles are set. Starting of the automatic reclosure function is allowed for at least the first cycle.
The action times are set as follows:

•

1st Reclosure: T Action = 0.2 s;

•

2nd Reclosure: T Action = 0.8 s;

•

3rd Reclosure: T Action = 1.2 s;

Since reclosure is ready before the fault occurs, the first trip of a time overcurrent protection following a fault
is fast, i.e. before the end of any action time. This starts the automatic reclose function. After unsuccessful
reclosure, the 2nd cycle would then become active; but the time overcurrent protection does not trip in this
example until after 1s according to its grading time. Since the action time for the second cycle was exceeded
here, the second cycle is blocked. The 3rd cycle with its parameters is therefore carried out now. If the trip
command appeared more than 1.2 s after the 1st reclosure, there would be no further reclosure.
Example 2: 3 cycles are set. Starting is only allowed for the first. The action times are set as in example 1. The
first protection trip takes place 0.5 s after starting. Since the action time for the 1st cycle has already expired
at this time, this cannot start the automatic reclose function. As the 2nd and 3rd cycles are not permitted to
start the reclose function they will also not be initiated. Therefore no reclosure takes place as no starting took
place.

Siemens SIPROTEC 4 7VK61, Manual

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