What is difference between earth leakage relay and
restricted earth fault relay ?
Answer Posted / alialewesy
earth leakage relay can not distinguish the fault location
so that it works for faults inside transformer winding &
outside transformer winding ( drawback)
REF protection has the advantage of distinguishing the
fault location .
it works only for earth faults inside the transformer
winding the transformer will be tripped only for earth
fault insid their winding
th only disadvantage of REF protection is that
it can not cover the whole winding . it protect only 80-85%
of transformer winding
for the reason of CT differences & saturation of CT
so that astand by protection is needed to protect the 15%
of the unprotected winding
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