ABB REC670 Applications Manual page 332

Section 14
Control
326
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.
1MRK 511 401-UUS A
Bay control REC670 2.2 ANSI
Application manual