2 Functions
138
7UT613/63x Manual
C53000-G1176-C160-2
2.3 Restricted Earth Fault Protection
The restricted earth fault protection detects earth faults in power transformers, shunt
reactors, neutral earthing transformers/reactors, or rotating machines, the starpoint of
which is led to earth. It is also suitable when a starpoint former is installed within a pro-
tected zone of a non-earthed power transformer. A precondition is that a current trans-
former is installed in the starpoint connection, i.e. between the starpoint and the earth-
ing electrode. The starpoint CT and the phase CTs define the limits of the protected
zone exactly. Restricted earth fault protection is not applicable to busbars.
7UT613/63x provides a second earth fault differential protection. The following func-
tion description refers to the 1st instance (address 13xx). The 2nd instance is set via
addresses 14xx.
2.3.1 Application Examples
Examples are illustrated in the Figures 2-50 to 2-56.
Figure 2-50 Restricted earth fault protection on an earthed transformer winding
Figure 2-51 Restricted earth fault protection on an earthed winding of a single-phase power
transformer
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