ABB REL650 Applications Manual page 311

1MRK 506 334-UUS A
Application manual
For the individual line breakers and auto-reclosing equipment, the "auto-reclosing open
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 open 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-reclosing function per line end. If auto-
reclosing functions are included in duplicated line protection, which means two auto-
reclosing functions 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-reclosing function per CB is recommended. Arranged
in such a way, sequential reclosing of the two CBs can be arranged with a priority circuit
available in the auto-reclose function. 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. Another advantage with the breaker connected auto-recloser is
that checking that the breaker closed before the sequence, breaker prepared for an auto-
reclose sequence and so on. is much simpler.
The auto-reclosing function performs three-phase automatic-reclosing with single-shot or
multiple-shots.
In power transmission systems it is common practise 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-reclosing function 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 also connected to inhibit the Auto-Reclose.
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-Reclosing function.
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
Section 11
Control
305