ABB Relion 670 Series Applications Manual page 288

Section 12
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 505 370-UUS Rev. K
Busbar protection REB670
Application manual