Application Guide - NP900 Series
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A996A
Figure 3.6.4.2-183. Autoreclosing shot settings, two requests and two shots are
initialized.
In this example for earth faults its own operating time settings are used and for
overcurrent time delay its set from autorecloser. Both fault types can initialize both of the
shots with different settings. If the fault evolves from earth fault AR2 to multi-phase fault,
auto-recloser will use AR1 settings for the reclosing. In this example the dead time in
between of the first and second shot is different due to need for give more time for the air
to cool and de-ionize in the case of overcurrent or multi-phase fault. If high set overcurrent
stage activates in any situation the autoreclosing sequence is ended. In this case final trip
shall be issued and the feeder closing will be locked by autorecloser. Closing of the
breaker will require manual reset of the autorecloser lock before attempting to close the
breaker. Manual reset can be applied from SCADA or locally from the HMI of the IED.
Following graphs present the principle signaling of the autorecloser in different cases
possible for this type of line. The graphs describe the available requests status,
autorecloser internal signal statuses, timer statuses, breaker controls from autorecloser
and breaker status signals.
Autorecloser operates closely with Object control and all of the breaker status and monitor
signals are forwarded from the selected Object to the autorecloser. Also circuit breaker
Open and Close signals are controlled through the dedicated Object. In cases if the
breaker cannot be closed due to it is not ready or closing is waiting for synchrocheck
allowance the wait state is forwarded to autorecloser so that it waits for Object to
acknowledge either successful closing or failure timeout. Similar situation can arise in
circuit breaker open command e.g. if the open is blocked due to SF6 gas leakage. In the
failure acknowledgements situations autorecloser is always put to lock-out state with
requirement for manual reset when the cause of the lock-out is cleared.
