what do you mean by earth fault in transformer?
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Answer Posted / shailesh aggarwal
Basically Earth faults are caused if high fault current
flows through the neutral of the transformers. This type of
fault arises mainly in Star connected transformers.Earth
faults are specified in many categories:
1. Restricted Earth faults(Inside the zone HT/LT side of
trafo) Connection are done b/t Phase CT & Neutral CT of
tranformer)Indicated as REF(64)
2. Standby Earth Faults(Directly linked with neutral of
trafo)connection only done b/t neutral CT.Indicated as SBEF
(51N).
Both the protection give signals to the numerical relays
and cause the tripping as earth faults and directly trip
the transformer.
Thus in order to save transformers a proper earthing is
required whether solid or usong NGRs.
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