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 / ramji
The differential protection is used for protecting the
transformer from internal winding fault,internal winding
shorts etc.,.It operates through three sets of CT's
connected in and out of transformer.It may or may not
operate during minor earth faults.REF is used to detect the
earth fault at restricted zone where its protection CT is
connected.It will surely operate during earth fault.But not
in windings short.
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