why will a REF protection not operate for a thourough faul that is the fault outside the protected zone as even in that case current unbalance will b there ?
Ref protection is an unit protection, which operates only for the internal faults. For external faults the differential protection will sense and operates before the REF prot. So REF doesn't operate for the external faults.
it is a zone protection or unit protection which operates when fault has taken place in particular zone or in unit,
for outside fault, there will be a current imbalance but this imbalance current will also return back throuh neutal of the zone, so current in the zone remains balanced even if fault has taken place outside the zone,
REF Protection
Re: REF Protection
