CHAPTER 5: SETTINGS
CONTROL ELEMENTS
F35 MULTIPLE FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
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5
5.8.11 Cold load pickup
SETTINGS
CONTROL ELEMENTS
COLD LOAD PICKUP
COLD LOAD PICKUP 1(6)
Cold load is the restoration of current into the system after being off. A cold load condition can be caused by a prolonged
outage of the load, by opening of the circuit breaker, or by a loss of supply even if the breaker remains closed. Upon the
return of the source, the circuit experiences inrush current into connected transformers, accelerating currents into motors,
and simultaneous demand from many other loads because the normal load diversity has been lost.
This feature can be used to change protection element settings when (by changing to another settings group) a cold load
condition is expected to occur. During the cold load condition, the current level can be above the pickup setting of some
protection elements, so this feature can be used to prevent the tripping that is otherwise caused by the normal 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 1 second, 200% after 2 seconds, and 150% after 3 seconds.
Figure 5-169: Typical cold load pickup characteristics
There are two methods to initiate operation of this feature.
The first initiation method is automatic response to a loss of the source to the feeder, by detecting that all phase currents
have declined to zero for some time. When zero current on all phases has been detected, a timer starts. This timer is set to
an interval after which it is expected the normal load diversity has been lost, so setting groups are not changed for short
duration outages. After the delay interval, the output operand is set.
The second initiation method is automatic response to an event that sets an operand, such as an operator-initiated virtual
input. This second method of initiation sets the output operand immediately.
Both initiating inputs can be inhibited by a blocking input. Once cold load pickup is in operation, the output operand
remains set until at least one phase of the load has returned to a level above 2% of CT nominal for the interval
programmed by the
ON-LOAD TIME BEFORE RESET
setting has expired. The reset delay interval is intended to be set to a
period until the feeder load has decayed to normal levels, after which other features can be used to switch setting groups.
COLD LOAD PICKUP 1
COLD LOAD 1
FUNCTION: Disabled
Range: Disabled, Enabled
COLD LOAD 1 PICKUP
SOURCE: SRC 1
Range: SRC 1, SRC 2, SRC 3, SRC 4, SRC 5, SRC 6
COLD LOAD 1 INIT:
Off
Range: FlexLogic operand
COLD LOAD 1 BLK:
Off
Range: FlexLogic operand
OUTAGE TIME BEFORE
COLD LOAD1: 1000 s
Range: 0 to 1000 s in steps of 1
ON-LOAD TIME BEFORE
RESET1: 100.000
Range: 0.000 to 1000 000.000 s in steps of 0.001
