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2 Functions
114
7ST6 Manual
E50417-G1176-C251-A3
Figure 2-32
Characteristic curve of the differential protection for defrosting
The characteristic can be configured with the following parameters:
Id>
Pickup value of the differential current
k
Characteristic slope
The knee-point of the characteristic is determined by the parameters k and Id>. The
value for Id> results from shunt currents which are independent of the defrosting cur-
rent, and which can occur in fault-free condition. Such currents can be caused by ca-
pacitive leakage currents, or by the magnetizing currents of power transformers
located upstream of the protected zone. The slope k to be set results from possible
amplitude or angle errors of the current transformers used.
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