GUID-92818F6B-4FB7-4D5C-AF64-36786F31AED8 V3 EN
Figure 224: Inrush current detection logic
Differential calculation
The operating principle is to calculate on both ends differential current from currents
entering and leaving the protection zone by utilizing the digital communication channels
for data exchange. The differential currents are almost zero on normal operation. The
differential protection is phase segregated and the differential currents are calculated
separately on both ends.
Communication
INCOMING
INCOMING
PROTECTED ZONE
RED 615 RED 615
GUID-E9D80758-16A2-4748-A08C-94C33997E603 V3 EN
Figure 225: Basic protection principle
The differential current I∆ (I
d
) of the protection relay is obtained on both ends with the
formula:
GUID-9C08695B-8241-4B74-AA2A-B64783F9C288 V2 EN (Equation 66)
The stabilizing current I
bias
(I
b
) of the protection relay is obtained on both ends with the
formula:
1MAC059074-MB A Section 4
Protection functions
615 series ANSI 465
Technical Manual
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