3
Application
The majority (about 80-85%) of MV overhead
line faults are transient and are automatically
cleared by momentarily deenergizing the line.
The rest of the faults (15-20%) can be cleared by
longer interruptions. Deenergizing of the fault
place for the desired period of time is imple-
mented by auto-reclose relays. Auto-reclose re-
lays are capable of clearing most of the faults. At
a permanent fault auto-reclosing is followed by
final tripping. A permanent fault has to be
located and cleared before the fault location can
be reenergized.
The auto-reclose module SPCT 5D54 can be
used for auto-reclosing together with any circuit
breaker suitable for auto-reclosing. The module
provides five programmable auto-reclose shots
which can perform from one to five successive
auto-reclosures of desired type and duration, for
instance, one high-speed and one delayed auto-
reclosure. When reclosing is initiatiated by start
of the protection, the auto-reclose module is
capable of tripping the circuit breaker finally in
a short operate time, if the fault still persists
when the last reclosure selected has been carried
out.
Fig. 1 illustrates a typical auto-reclose situation,
where one auto-reclose shot has been performed
after the fault was detected. In case a) the auto-
reclose shot is initiated by a start signal of the
protection, after the start delay time has elapsed.
In case b) the auto-reclose shot is initiated by a
trip signal of the protection. In both cases the
auto-reclose sequence was successful.
Auto-reclose initiated
by start of protection
Auto-reclose initiated
by trip of protection
Protective relay
Auto-reclose relay
Circuit breaker (CB)
Protective relay
Auto-recloser
Circuit breaker (CB)
Instant of fault
Start signal
Start delay time
CB open
pulse
Open
Close
Dead time
CB close
pulse
Start signal
Open
Close
Dead time
CB close
pulse
Trip
signal
Reclaim time
Shot 1
Reclaim time
Shot 1
Operating time
Operating time
a)
b)
Fig. 1. Signal scheme illustrating the auto-reclose operation
Summary of Contents for SPAA 341 C /E351
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