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

Functions
2.5 Restricted Earth Fault Protection (optional)
SIPROTEC, 7SD610, Manual
C53000-G1176-C145-6, Release date 02.2011
82
2.5 Restricted Earth Fault Protection (optional)
The restricted earth fault protection detects earth faults in power transformers, the starpoint of which is earthed.
It is also suitable when a starpoint former is installed within a protected zone of a non-earthed power transform-
er. 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 star-
point current of the transformer side to be protected.
Figure 2-25 Restricted earth fault protection on an earthed transformer winding
Figure 2-26 Earth fault differential protection at a delta winding with earthed artificial starpoint
(neutral earthing transformer, zigzag reactor)