pollution etc. can influence the required dead time. Some users apply Delayed Auto-
Reclosing (DAR) with delays of 10s or more. The delay of reclosing shot 2 and
possible later shots are usually set at 30s or more. A check that the CB duty cycle can
manage the selected setting must be done. The setting can in some cases be restricted
by national regulations. For multiple shots the setting of shots 2-5 must be longer than
the circuit breaker duty cycle time.
tSync
, Maximum wait time for synchronizationcheck
The time window should be coordinated with the operate time and other settings of the
synchronization check function. Attention should also be paid to the possibility of a
power swing when reclosing after a line fault. Too short a time may prevent a
potentially successful reclosing.
A typical setting may be 2.0 s. In cases where synchronization is used together with
auto-recloser the time must be set to 100-600s to allow operation at minimum
frequency difference.
tTrip
, Long trip pulse
Usually the trip command and start auto-reclosing signal reset quickly as the fault is
cleared. A prolonged trip command may depend on a CB failing to clear the fault. A
trip signal present when the CB is reclosed will result in a new trip. At a setting
somewhat longer than the auto-reclosing open time, this facility will not influence the
reclosing. A typical setting of tTrip could be close to the auto-reclosing open time.
tInhibit
, Inhibit resetting delay
A typical setting is tInhibit = 5.0 s to ensure reliable interruption and temporary
blocking of the function. Function will be blocked during this time after the tinhibit
has been activated.
tReclaim
, Reclaim time
The Reclaim time sets the time for resetting the function to its original state, after
which a line fault and tripping will be treated as an independent new case with a new
reclosing cycle. One may consider a nominal CB duty cycle of for instance, O-0.3sec
CO- 3 min. – CO. However the 3 minute (180 s) recovery time is usually not critical
as fault levels are mostly lower than rated value and the risk of a new fault within a
short time is negligible. A typical time may be tReclaim = 60 or 180 s dependent of
the fault level and breaker duty cycle.
StartByCBOpen
The normal setting is Off. It is used when the function is started by protection trip
signals.
FollowCB
The usual setting is Follow CB = Off. The setting On can be used for delayed reclosing
with long delay, to cover the case when a CB is being manually closed during the
“auto-reclosing open time” before the auto-reclosing function has issued its CB
closing command.
1MRK 505 291-UEN A Section 10
Control
209
Application manual
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