GE Feeder Management Relay 750

GE Multilin 750/760 Feeder Management Relay 5-103
5 SETPOINTS 5.8 S7 CONTROL
5
5.8.4 COLD LOAD PICKUP BLOCKING
PATH: SETPOINTS ÖØ S7 CONTROL ÖØ COLD LOAD PICKUP
The 750/760 can be programmed to block instantaneous overcurrent elements and to raise the pickup level of time over-
current elements when a cold load condition is detected. Under normal operating conditions, the actual load on a feeder is
less than the maximum connected load, since not all consumers require maximum load at the same time. When such a
feeder is closed after a prolonged outage, the feeder inrush and motor accelerating current may be above some protection
settings. Without historical data on a particular feeder, some utilities assume an initial cold load current of about 500% of
normal load, decaying to 300% after one second, 200% after 2 seconds, and 150% after 4 seconds. See the figure below.
A cold load condition is initiated and overcurrent settings are altered when all phase currents drop below 5% of the nominal
current for an amount of time greater than the
OUTAGE TIME BEFORE COLD LOAD setpoint. The cold load condition can also
be immediately initiated by asserting the logic input function ‘Cold Load Pickup’. Overcurrent settings are returned to nor-
mal after any phase current is restored to greater than 10% of nominal and then a timer of duration equal to
COLD LOAD
PICKUP BLOCK TIME
expires.
 COLD LOAD PICKUP
 [ENTER] for more
COLD LOAD PICKUP
FUNCTION: Disabled
Range: Disabled, Alarm, Latched Alarm, Control
COLD LOAD PICKUP
RELAYS (3-7): -----
Range: Any combination of 3 to 7 Auxiliary relays
OUTAGE TIME BEFORE
COLD LOAD: 100 min
Range: 1 to 1000 min. in steps of 1
COLD LOAD PICKUP
BLOCK TIME: 5 s
Range: 1 to 1000 s in steps of 1
PHASE INST OC 1
BLOCKING: Disabled
Range: Disabled, Enabled
NEUTRAL INST OC 1
BLOCKING: Disabled
Range: Disabled, Enabled
GND INST OC
BLOCKING: Disabled
Range: Disabled, Enabled
NEG SEQ INST OC
BLOCKING: Disabled
Range: Disabled, Enabled
PHASE TIME OC 1
RAISED PICKUP: 0%
Range: 0 to 100% in steps of 1
NEUTRAL TIME OC 1
RAISED PICKUP: 0%
Range: 0 to 100% in steps of 1
GND TIME OC
RAISED PICKUP: 0%
Range: 0 to 100% in steps of 1
NEG SEQ TIME OC
RAISED PICKUP: 0%
Range: 0 to 100% in steps of 1
SELECT SETPOINT
GROUP: Active Group
Range: Group 1, Group 2, Group 3, Group 4, Active
Group
ENTER
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Courtesy of NationalSwitchgear.com