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:
•
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 recloser out of service or circuit breaker 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 used as an alternative when the autorecloser is shared with another
subsystem. This provides a fail safe connection so that even a failure in the IED with
the auto-recloser will mean that the other sub-system will start a three-pole trip.
1MRK 505 370-UUS A
Section 12
Control
Busbar protection REB670 2.2 ANSI
317
Application manual
Summary of Contents for RELION REB670
Page 1: ...RELION 670 SERIES Busbar protection REB670 Version 2 2 ANSI Application manual ...
Page 2: ......
Page 24: ...18 ...
Page 40: ...34 ...
Page 72: ...66 ...
Page 102: ...96 ...
Page 266: ...260 ...
Page 272: ...266 ...
Page 290: ...284 ...
Page 432: ...426 ...
Page 542: ...536 ...
Page 552: ...546 ...
Page 553: ...547 ...