Answer / k.prakashchandra

EFR is for general earth fault and REFR is for earth fault
within the area covered or for a certain equipment e.g.
tranformer.

Answer / nur.asidik

EF/SEF/50N/51N/51G can be detected by core balance CT or by vector summation of line CT(residual)
64REF is by comparing current flowing at TR neutral CT with residual CT at line CT,

Answer / harnish desai

REF will detect earth fault within its equipoment & work on
principal of vector sum of Ir + Iy + Ib + In = 0.
Ef relay will sense current in only neutral CT & operate
relay.

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