(a) + (e) - (d) = 50 ms + 280 ms - 85 ms = 245 ms, to allow de-ionising
In practice a few additional cy
cles would be added to allow for tolerances, so Dead Time 1 could be set to 300 ms
or greater. The overall system dead time is found by adding (d) to the chosen settings then subtracting (a). This
gives 335 ms.
A typical de-ionising time value for single-phase trip on a 220 kV line is 560 ms, so the 1 Pole Dead Time could be
chosen as 600 ms or greater. The overall system dead time is found by adding (d) to the chosen settings then
subtracting (a). This gives 635 ms.
6.3 RECLAIM TIME SETTING GUIDELINES
Several factors influence the choice of the reclaim timer, such as:
● F
ault incidence/Past experience: Small reclaim times may be required where there is a high incidence of
recurrent lightning strikes to prevent unnecessary lockout for transient faults.
● Spring charging time: For high speed Autoreclose the reclaim time may be set longer than the spring
charging time. A minimum reclaim time of more than 5s may be needed to allow the circuit breaker time to
recover after a trip and close before it can perform another trip-close-trip cycle. This time will depend on the
duty (rating) of the circuit breaker. For delayed Autoreclose this may not be needed as the dead time can be
extended by an extra circuit breaker healthy check / Autoreclose Inhibit Time window time if there is
insufficient energy in the circuit breaker.
● Switchgear Maintenance: Excessive operation resulting from short reclaim times can mean shorter
maintenance intervals.
When used in conjunction with distance protection, the Reclaim Time setting is generally set greater than the zone
2 delay.
Chapter 7 - Autoreclose P54A/B/C/E
180 P54xMED-TM-EN-1
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