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.
When Single and/or three phase auto reclosing is considered, there are a number of cases
where the tripping shall be three phase anyway. For example:
Section 15 1MRK 506 369-UUS -
Control
656 Line distance protection REL670 2.2 ANSI
Application manual
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