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100000
10000
1000
100
10
0.1
1
10
100
Current (kA, RMS)
Figure 14. Eagle VG4 Life Curve
Setting Application Example
To program the open KSI alarm setting, the available fault current at the recloser location
is required. To obtain this value, the total line impedance can be used from the
substation to the point where the recloser is installed. Using this impedance and line
voltage, available fault current can be calculated using I=V/R calculation.
With a 12.47kV circuit and total line impedance of 5A where the recloser is installed, the
total available fault current is roughly 2500A. Looking at 2500A on the Eagle Life Curve,
the number of operations available are approximately 2400. Since the KSI values are
normalized by a factor of 100, the alarm can be set at (2500/100)*2400 = 60000.
4.4.4. Cold Load Pickup
Cold load pick-up problems occur during severe cold or hot weather. When power is
disrupted in the winter, many families leave their heating systems and appliances on.
When power is restored, those heating systems cause a huge drain on the power lines and
can cause line protection equipment to take the overloaded lines off line because the
heavy load acts the same as a fault on the line. Cold-load pick-up problems also occur in
the summer when families and businesses are running air-conditioning units and heat
pumps. Cold-load pick-up problems are prevented when customers turn off their electric
heating or air-conditioning systems, lights and appliances and then, after power has been
restored, turn them back on over a period of time.
The cold load pickup is used to block unintentional tripping of protection element due to
sudden current detected after the recloser circuit has been open for a specified period.
Cold load pickup is not operational during a normal reclose sequence.
For overcurrent function to be blocked by Cold Load Pickup, it is required that setting CLP
Apply is enabled in respective protection function.
25
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