ABB REB670 Applications Manual page 310

Section 12
Control
304
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.
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:
• Evolving fault where the fault during the dead-time spreads to another phase. The
other two phases must then be tripped and a three phase dead-time and auto-reclose
initiated
• Permanent fault
• Fault during three phase dead-time
• Auto-reclose out of service or CB not ready for an auto-reclosing cycle
"Prepare three-pole tripping" is then used to switch the tripping to three-pole. This signal
is generated by the auto-recloser and connected to the trip function block and also
connected outside the IED through IO when a common auto-recloser is provided for two
sub-systems. An alternative signal "Prepare 1 Pole tripping" is also provided and can be
1MRK 505 337-UUS -
Application manual