ABB Relion 670 Series Applications Manual page 298

Section 14
Control
For the individual line breakers and auto reclosing equipment, the auto reclosing dead time
expression is used. This is the dead time setting for the auto recloser. During simultaneous
tripping and reclosing at the two line ends, auto reclosing dead time is approximately equal to the
line dead time. Otherwise these two times may differ as one line end might have a slower trip than
the other end which means that the line will not be dead until both ends have opened.
If the fault is permanent, the line protection will trip again when reclosing is attempted in order to
clear the fault.
It is common to use one automatic reclosing function per line circuit breaker (CB). When one CB
per line end is used, then there is one auto- recloser per line end. If auto reclosers are included in
duplicated line protection, which means two auto reclosers per CB, one should take measures to
avoid uncoordinated reclosing commands. In breaker-and-a-half, double-breaker and ring bus
arrangements, two CBs per line end are operated. One auto recloser per CB is recommended.
Arranged in such a way, that sequential reclosing of the two CBs can be arranged with a priority
circuit available in the auto recloser. In case of a permanent fault and unsuccessful reclosing of the
first CB, reclosing of the second CB is cancelled and thus the stress on the power system is
limited.
The auto recloser can be selected to perform single-phase and/or three-phase automatic
reclosing from several single-shot to multiple-shot reclosing programs. The three-phase auto
reclosing dead time can be set to give either High-Speed Automatic Reclosing (HSAR) or Delayed
Automatic Reclosing (DAR). These expressions, HSAR and DAR, are mostly used for three-phase
auto reclosing as single-phase auto reclosing is always high speed to avoid maintaining the
unsymmetrical condition. HSAR usually means a dead time of less than 1 second.
In power transmission systems it is common practice to apply single- and/or three-phase, single-
shot auto reclosing. In sub-transmission and distribution systems tripping and auto reclosing are
usually three-phase. The mode of automatic reclosing varies however. Single-shot and multi-shot
are in use. The first shot can have a short delay, HSAR, or a longer delay, DAR. The second and
following reclosing shots have a rather long delay. When multiple shots are used the dead time
must harmonize with the breaker duty-cycle capacity.
Automatic reclosing is usually started by the line protection and in particular by instantaneous
tripping of such protection. The auto recloser can be inhibited (blocked) when certain protection
functions detecting permanent faults, such as shunt reactor, cable or busbar protection are in
operation. Back-up protection zones indicating faults outside the own line are typically connected
to inhibit the auto recloser.
Automatic reclosing should not be attempted when closing a CB and energizing a line onto a fault
(SOTF), except when multiple-shots are used where shots 2 etc. will be started at SOTF. Likewise a
CB in a multi-breaker busbar arrangement which was not closed when a fault occurred should not
be closed by operation of the auto recloser. Auto reclosing is often combined with a release
condition from synchronism check and dead line or dead busbar check. In order to limit the stress
on turbo generator sets from auto reclosing onto a permanent fault, one can arrange to combine
auto reclosing with a synchronism check on line terminals close to such power stations and
attempt energizing from the side furthest away from the power station and perform the
synchronism check at the local end if the energizing was successful.
Transmission protection systems are usually sub-divided and provided with two redundant
protection IEDs. In such systems it is common to provide auto reclosing in only one of the sub-
systems as the requirement is for fault clearance and a failure to reclose because of the auto
recloser being out of service is not considered a major disturbance. If two auto reclosers are
provided on the same breaker, the application must be carefully checked and normally one must
be the master and be connected to inhibit the other auto recloser if it has started. This inhibit can,
for example, be done from an auto recloser for 3-phase operation in progress signal.
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1MRK 511 401-UUS F
Bay control REC670
Application manual