Autoreclose Zone Coordination - GE 750 Instruction Manual

14.8 AUTORECLOSE (760 ONLY)
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 settings on the 760 each time the recloser oper-
ates. To ensure that protection coordination 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 mag-
nitude, due to a recloser opening. After the first detection of an external reclose, the shot counter is incre-
mented by one, protection settings 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
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reset mechanism.
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
NOTE
reach lockout.
ZONE COORDINATION
[ENTER] for more
ZONE COORDINATION
FUNCTION: Disabled
PHASE CURRENT
INCREASE: 1.00 x CT
NEUTRAL CURRENT
INCREASE: 1.00 x CT
MAX FAULT CLEARING
TIME: 10 s
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Courtesy of NationalSwitchgear.com
The Autoreclose Zone Coordination setpoints path is:
\ SETPOINTS \ S7 CONTROL \ AUTORECLOSE \ ZONE COORDINATION
Range: Enabled, Disabled
Enables or disables the autoreclose zone coordination scheme.
Range: 0.05 to 20.00 in steps of 0.01 x CT
This setting selects the minimum phase current step increase that signifies a
downstream fault. This current may be quite low for an end fault on a long
feeder with a weak source.
Range: 0.05 to 20.00 in steps of 0.01 x CT
This setting selects the minimum neutral current step increase that signifies a
downstream fault. This current may be quite low for an end fault on a long
feeder with a weak source.
Range: 1 to 1000 in steps of 1 s
This setting 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 oper-
ate the decreasing current detector. This delay must be set longer than the
maximum fault clearing time on the recloser.
750/760 Feeder Management Relay

14.8.5 AUTORECLOSE ZONE COORDINATION

14 S7 CONTROL
GE Power Management