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Functions
2.17 Automatic Reclosure Function (optional)
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
321
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. It is therefore recommended to
use action times in conjunction with the distance protection.
The automatic reclosure function of the 7SD5 can be operated with or without action times (configuration pa-
rameter
AR control mode , address 134 , see Section 2.1.1.3). No starting signal is necessary from the pro-
tection 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 reclo-
sure, 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.
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
function, the 1st cycle is practically skipped.
Operating modes of the automatic reclosure function
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
reclosure function operating mode selected when determining the function scope and the resulting signals of
the starting protection functions.
In control mode
TRIP...
(With TRIP command ...), 1-pole or 1-/3-pole reclose cycles are possible if the device
and the circuit breaker are suitable. In this case, different dead times (for every AR cycle) are possible after 1-
pole tripping and after 3-pole tripping. The protection function that issues the trip command determines the type
of trip: 1-pole or 3-pole. The dead time is controlled dependent on this.