Application Guide - NP900 Series
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A996A
Arcing time can be used for controlling the autoreclosing in cases protection function Start
signal is making the requests. In case if the request (start) activates during the Reclaim
time the Arcing time calculation starts and if fault persists autorecloser shall continue to
next stage. If Arcing time calculation starts but stops before the set time have been used
then Reclaim time calculation continues normally and when it is elapsed autorecloser shall
return to either General Reclaim time or into Ready mode and the shot is considered as
successful. Arcing time counter is not resetting from the request drop off during the
Reclaim time and every time the request is activated (e.g. protection function starts) the
arcing time counter is deducted by the time request is on. This means that the time set to
Arcing time parameter means cumulative time of start allowed in Reclaim time before
decision is made that the shot is failed or succeeded.
In case the autoreclosing is used in the time coordinated network protected by IDMT time
characteristics and the relays are old mechanical types which have also current
dependent release time the operation of the protection selectivity has to be guaranteed by
allowing all of the relays timing devices reset completely during the dead time so that the
correct time discrimination is maintained after reclosing to the fault. Time required for
mechanical IDMT relay to reset may be even 10 s in some cases. When short dead times
are required the relays should reset almost instantaneously so that the current dependent
time grading operates as expected. For these cases in the autorecloser is possible to set
certain discrimination time instead of arcing time, which starts simultaneously with reclaim
time and if during this discrimination time any new reclosing requests are made the
recloser will halt and let the protection devices operate based into their settings and does
not interfere on the operation of the protection functions or the breaker. This means also
that further reclosing are not made before the autorecloser is reset manually and the
breaker shall remain open until it is manually closed.
3.6.4.11
A
UTORECLOSER
IO
Main outputs of the autorecloser function are Object open and Object close control
signals. In addition to these output controls the function will report the recloser status
information to be used in the logics or LED indications as well as applied operations.
Setting parameters are static inputs for the function which are changed only by user input
in the setup phase of the function.
Inputs for the function are binary recloser request signals, blockings and controlling
signals, controlled object monitoring and status signals. The function registers its
operation into 12 last time-stamped registers and also generates general time stamped
ON/OFF events to the common event buffer from each of the two output signal as well as
