Dec 4, 2013

Restricted Earth Fault Relay



earth fault relay
Restricted earth fault relay is that relay which might be outlined as half of differential relay. Figure shows an illustration for the restricted earth fault relay. This definition is owing to its connection. This is often relay compare current flow in:

1) The neutral track of Instrument Transformer connected on the star aspect of power transformer:

2) Current flow within the Instrument Transformer (CT) connected on the star point of the Transformer.

  • For inner faults (flanked by the 2 CT’s), there's differential current that is reworked to Volt by a really large shunt resister (metrosil) and this value of Volt is sufficient for operation of the relay.
  • For outward faults (ie. outbound feeder’s faults) the differential current during this case is zero and also the relay won't operate, and no tripping for circuit breakers can occur.


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