Eaton EDR 3000 Installation, Operation And Maintenance Manual page 515

Via the pre shot (fast trip), the AR-module is able to trip the breaker ahead of
the protection stage that has activated the AR-module. As a general rule, a
fast trip is either issued before the first reclosure attempt or after the last
permitted reclosure attempt.
1. At the beginning of the sequence, a "Pre shot" (Fast trip) is executed
before the time overcurrent protection element of any device on the line
completely times out. Purpose: to clear the fault before any of the
circuit protection trips or blows open. A short time after the pre-shot
occurs, the breaker can be re-closed into the line and all circuits
connected on the line will still be energized. 80%-90% of the faults are
not permanent. After a period from 0.5 up to 1 sec., the line is probably
no longer faulty and the complete line can be re-energized. If the line is
still faulty, segments of the line will be switched off selectively by the
time over-current protection module as a result of the system
coordination.
2. A Pre shot (Fast trip) at the end of the reclosure sequence occurs after
the last permitted reclosure shot. Purpose: To prevent unnecessary
damage from the electrical equipment in case of permanent faults. If
the last reclosure attempt is executed and the fault is still present, then
the breaker can be tripped quickly before the time overcurrent
protection module has completely timed out.
EDR-3000
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