why we use REF and Differential Protection in one
transformers?my doubt is both protections are operated in
internal fault only.why we want to use 2 protections?please
clarify.

Answer Posted / gunasekaran

both are using for internal fault but differential
protection only sensitive up to 92% winding of the
transformer if any fault occur in balance 8% winding diff is
not operating so we r using REF protection

Is This Answer Correct ?    11 Yes 7 No



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