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Cold load protection (CLP)
The function of cold load protection (CLP) can have a number of disparate groups for setting.
The CLP can switch a group setting from one operation to another operation at which
protection functions in the IED are required to shift their settings from steady state to
particular state. For instance, the setting group for the particular state is good for a period
after energizing the system.
In the steady state operation, the load current through a transmission-line is smaller
than the total of the rated loads that connected to the transmission-line. The load current can
reach as high as times of the maximum load current for a moment when the entire loads are
energized after a long interruption, but the load current can decreases within three or four
seconds. It is accounted that the load current at the energizing time is 1.5 times larger than a
normal peak load. Thus, it is necessary for some protective functions to have a few setting
groups that discriminate between the inrush current on cold load restoration and the fault
current. For instance, the function of overcurrent protection (OC) with the CLP is immune
during the inrush period. The OC is discussed separately. (See Chapter 2.1)
The CLP can have eight setting groups for cold load state in order that the CLP can
follows the transition from one state to another state. Thus, the CLP can make some protective
functions switch to another higher setting group including time delay. The CLP also can halt
with setting. The group selection of the CLP is performed with scheme switch [CLP-SG].
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6F2T0207 (0.01)
GRE200 (5,6)
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