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these systems.
Reclaim Time [TREADY]
The reclaim time of the ARC function and making it ready for the next cycle of operation
requires certain considerations.
Where the incidence of recurrent lightning strikes is experienced, a shorter reclaim time
will prevent the ARC function going into an unnecessary lock out. On the other hand, caution
is required when considering the exposure of the CB to an excessive number of ARC cycles
caused by recurrent faults thus increasing the frequency of maintenance that will be required.
The time necessary for the CB to be ready for the next cycle of ARC will determine the
minimum time required in determining the setting of the reclaim time for the ARC function.
The criteria for setting the reclaim time is described in (ii)-3 below.
Inhibiting or blocking the ARC function
The ARC function should be blocked for protection operations from thermal overload protection
(THM), broken conductor protection (BCD), circuit breaker failure protection (CBF) and switch
on to fault (SOTF-OC) functions.
Setting example
(ii)
Input data
◆ CB open-close cycle:
◆ CB opening time (trip coil energized to arc interruption):
◆ CB closing time (close command to CB contacts make):
◆ Protection operation time (pick up to operation):
◆ Protection resetting time:
◆ De-ionization time of fault arc path:
◆ Maximum dead time allowed from stability consideration: 500ms
◆ Trip mechanism reset time (if any):
Not applicable in this case (e.g. spring charged mechanism, closing operation
automatically charges the tripping spring)
Note:
1. Stability criterion may not be applicable for a highly interconnected power
system where loss of one line does not endanger system stability.
2. Stability criterion will not apply to radial distribution feeders with no
downstream generating source.
- 253 -
6F2T0207 (0.01)
OCO-0.3s-CO-30s
3 cycles; 60ms (for 50Hz
system)
80ms
<45ms
<30ms
125ms
GRE200 (5,6)
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