Siemens SIPROTEC 7SD610 - Restricted Earth Fault Protection (Optional); Application Examples

2 Functions
80
7SD610 Manual
C53000-G1176-C145-4
2.5 Restricted Earth Fault Protection (optional)
The restricted earth fault protection detects earth faults in power transformers, the
starpoint of which is led to earth. It is also suitable when a starpoint former is installed
within a protected zone of a non-earthed power transformer. A precondition is that a
current transformer is installed in the starpoint connection, i.e. between the starpoint
and the earthing electrode. The starpoint CT and the phase CTs define the limits of the
protected zone exactly.
2.5.1 Application Examples
Figures 2-25 and 2-26 show two application examples. A prerequisite is that the I4
transformer detects the starpoint current of the transformer side to be protected.
Figure 2-25 Restricted earth fault protection on an earthed transformer winding
Figure 2-26 Restricted earth fault protection on a non-earthed transformer winding with
neutral reactor (starpoint former) within the protected zone
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