Balanced Earth Fault Protection

The balanced earth fault protection scheme is mainly used for protection of small generator where differential and self-balanced protection systems are not applicable. In a small generator, the neutral end of the three phase windings is connected internally to a single terminal. So the neutral end is not available, and protection against earth fault  is provided by using the balanced earth protection scheme. Such scheme does not provide protection against phase-to-phase fault until and unless they develop into earth faults.

Connection of Balanced Earth Fault Protection Scheme

In this scheme, the current transformers are mounted on each phase. Their secondary is connected in parallel with that of CT mounted on a conductor joining the star point of the generator to earth. A relay is connected across the secondaries of the CTs.