As Lawrence Lile mentioned, utility company's set their tripping and
reclosing schemes differently.  It varies even at a single utiltiy
depending if the line is rural or urban, overhead or underground, and on
the available close-in and end-of-line fault current.

I typically set overhead distribution lines with three trips to lockout.
The first trip used an instantaneous trip time that would trip for
phase-to-phase and phase-to-ground faults, with a fast reclose.  The
purpose of this was clear temporary faults, preserve fuses, and restore
service quickly.

Subsequent trips would be on timed-current curves.  This was done to force
downstream fuses or line reclosers to open and isolate the fault.  Reclose
times were longer as well.  After a total of three attempts, the breaker
would be locked open.

On underground feeders, we would trip once and lockout.  If there is a
fault on that system, something is really bad and reclosing would simply
cause mroe damage.

Mark Peterson

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