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.
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Answer Posted / munish
REF 64T is used for protect the 95% winding of T/F.it sens
only the internal fault of T/F and 51NT circulating earth
fault relay used for detect the other area.
87T diff. is act only when the difference B/W both side
current is more than setting value
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