ABB REC650 Applications Manual page 206

Section 10
Control
200
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
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 Autorecloser for 3-
phase operation(SMBRREC ,79) In progress.
1MRK 511 286-UUS A
Application manual