2.12 Automatic Reclosure Function
129
7ST6 Manual
E50417-G1176-C251-A3
Until the set maximum number of permissible auto-reclose cycles has been reached,
the reclaim time is reset with every new trip command after reclosure and started
again with the next close command.
If one of the reclosing attempts is successful, i.e. the fault disappeared after reclosure,
the blocking time expires and the automatic reclosing system is reset. The fault is
cleared.
If none of the cycles is successful, the short-circuit protection initiates a final trip after
the last permissible reclosure, following a protection stage active without auto-reclo-
sure. The auto reclose function is blocked dynamically (see also above under margin
heading „Blocking of Auto-reclosure“).
Interaction with the
Synchro-check
An activated external or internal synchro-check function may lead to an undesired ex-
tension of the dead time.
To prevent the automatic reclosure system from assuming an undefined state, the ex-
tension of the dead time is monitored. The extension time
T-DEAD EXT.
is started
when the regular dead time has expired. When it has expired, the auto reclose function
is blocked dynamically during 500 ms.
The auto reclose function resumes normal state when the blocking time has expired
and new blocking conditions do not apply.
Controlling the In-
ternal Automatic
Reclosure by an Ex-
ternal Protection
Device
If the 7ST6 is equipped with the internal auto reclose function, this can also be con-
trolled by an external protection device. This is useful for example for line ends with
redundant protection or back-up protection when the second protection is used for the
same line end and is to work with the automatic reclosure function integrated in the
7ST6.
Specific binary inputs and outputs must be considered in this case. It must be decided
whether the internal auto-reclosure is to be controlled by the pickup or by the trip
command of the external protection.
The following inputs and outputs are recommended to be used for the auto reclose
function:
The auto reclose function is started via the binary inputs:
2711
„>AR Start“
General
pickup,
2746
„>Trip for AR“
Trip command for automatic reclosure.
Automatic reclosure is controlled by the trip command. The external general pickup
signal is only needed for starting the action times.
If the external protection device has dependent tripping zones, additional binary inputs
for zone control are required.
Figure 2-39 shows as a connection example the interconnection between the internal
automatic reclosure of 7ST6 and an external protection device.
www
. ElectricalPartManuals
. com