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172
Automatic reclosing function (AR)
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Automatic reclosing (AR) is a well-established method to restore the service of a power
line after a transient line fault. The majority of line faults are flashover arcs, which are
transient by nature. When the power line is switched off by operation of line protection
and line breakers, the arc de-ionises and recovers voltage withstand at a somewhat vari-
able rate. So a certain line dead time is needed. But then line service can resume by the
auto-reclosing of the line breakers. Select the length of the dead time to enable good
probability of fault arc de-ionisation and successful reclosing.
For the individual line breakers and auto-reclosing equipment, the Auto-reclose open
time (AR open time) expression is used. At simultaneous tripping and reclosing at the
two line ends, Auto-reclose open time equals approximaltely the dead time of the line.
Otherwise these two times may differ.
In case of a permanent fault, the line protection trips again at reclosing to clear the fault.
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