5-124 750/760 Feeder Management Relay GE Multilin
5.8 S7 CONTROL 5 SETPOINTS
5
e) AUTORECLOSE ZONE COORDINATION
PATH: SETPOINTS ÖØ S7 CONTROL ÖØ AR ÖØ ZONE COORDINATION
The 760 autoreclose scheme can be programmed to maintain coordination of overcurrent elements with a downstream
recloser. If a downstream recloser is programmed to use different protection settings for different reclose shots, it may be
necessary to change the protection setpoints on the 760 each time the recloser operates. To ensure that protection coordi-
nation is maintained, each 760 reclosure shot must be coordinated with each downstream recloser shot. In addition, the
760 reclose shot counter must always match the recloser shot counter. When a fault occurs downstream of the recloser
and the 760 feeder breaker does not trip and reclose, the 760 reclosure shot counter must still be incremented.
Once enabled, this scheme assumes an external reclose operation has occurred when the feeder phase or neutral current
exhibits a step increase in magnitude, due to fault current, followed by a step decrease in magnitude, due to a recloser
opening. After the first detection of an external reclose, the shot counter is incremented by one, protection setpoints are
changed, and the autoreclose scheme reset timer is initiated.
If the fault is permanent and the recloser continues to trip and reclose, the coordination feature will continue to increment
the shot counter. If this continues to the maximum number of shots programmed in the 760, the autoreclose scheme will go
to lockout. If the fault is transient, then the autoreclose scheme and shot counter will eventually be reset by the normal reset
mechanism.
The
PHASE CURRENT INCREASE and NEUTRAL CURRENT INCREASE setpoints select the minimum phase and neutral current
step increases that signify downstream faults. These currents may be quite low for an end fault on a long feeder with a
weak source. The
MAX FAULT CLEARING TIME setpoint is intended to reset the memory of an increasing current caused by
an increase in feeder load since the new load current will not drop to operate the decreasing current detector. This delay
must be set longer than the maximum fault clearing time on the recloser.
For correct operation of the coordination scheme, the 760 instantaneous protection elements must be set to have
time delays longer than the maximum fault clearing time of the downstream recloser. In addition, the autoreclose
reset timer must be set longer than the maximum time for the recloser to reach lockout.
îš„ ZONE COORDINATION
îš„ [ENTER] for more
ZONE COORDINATION
FUNCTION: Disabled
Range: Enabled, Disabled
PHASE CURRENT
INCREASE: 1.00 x CT
Range: 0.00 to 20.00 x CT in steps of 0.01
NEUTRAL CURRENT
INCREASE: 1.00 x CT
Range: 0.00 to 20.00 x CT in steps of 0.01
MAX FAULT CLEARING
TIME: 10 s
Range: 1 to 1000 s in steps of 1
ENTER
ESCAPE
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NOTE
Courtesy of NationalSwitchgear.com
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