Siemens Siprotec 7VK61 Manual page 45

Those protection and monitoring functions in the device which do not respond to short-circuits or similar con-
ditions (e.g. an overload protection) do not initiate the automatic reclosure function because a reclosure will be
of no use here. The breaker failure protection must not start the auto-reclosure either.
Action Times
It is often desirable to neutralize 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. It is therefore recommended to
use action times in conjunction with the distance protection.
The automatic reclosure function of the 7VK61 can be operated with or without action times (configuration pa-
rameter AR control mode, address 134, see section 2.1.1.2). No starting signal is necessary from the ex-
ternal protection devices that operate without action time. Starting takes place as soon as the first trip command
appears.
When operation 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 reclosure function). If no trip command is present before the action time expires,
the corresponding reclose cycle is not carried out.
For each reclosure cycle, you may set whether or not it allows the initiation. Following the first general pickup,
only the action times of those cycles that are set such that they may start off the recloser are considered since
the other cycles are not allowed to be the first cycle under any circumstances. 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 deter-
mine which reclose cycles are executed depending on the time used by the protection function to trip as the
following examples with time overcurrent protection show.
Example 1: 3 cycles are set. Starting of the auto-reclosure 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. The automatic reclosure function is therefore started (the first cycle
is initiated). After unsuccessful reclosure the 2nd cycle would then become active; but the time overcurrent pro-
tection would not trip in this example until after 1s according to its grading time. Since the action time for the
second cycle was exceeded here, it is blocked. The 3rd cycle with its parameters is therefore carried out now.
If the trip command only appeared more than 1.2s after the 1st reclosure, there would have been 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.
Example 3: 3 cycles are set. At least the first two cycles are set such that they can start the recloser. 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, it cannot start the automatic reclosure function, but the 2nd cycle,
for which initiating is allowed, is activated immediately. This 2nd cycle therefore starts the automatic reclosure
circuit, the 1st cycle is practically skipped.
Operating modes of the automatic reclosure
The dead times — these are the times from elimination of the fault (drop off of the trip command or signalling
via auxiliary contacts) to the initiation of the automatic close command — may vary depending on the automatic
SIPROTEC, 7VK61, Manual
C53000-G1176-C159-3, Release date 05.2009
2.2 Automatic reclosure function (optional)
Functions
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