Answer / sukhvinder

differential relay which operates on two or more similar
quantities i.e voltage,current.

in this relay under normal condition, no voltage flow
through coil i.e vi+v2=0 but in abnormal the differnce of
two voltage i.e v1+v2 will not equal to zero. so that
voltage will flow through the coil further protection of
equipment/devie/system etc.

Answer / akhilesh

suppose pri side of pt(3 no's) is connected to any 3 phase
winding n sec of pt is open delta or connected to relay. in
balance cond Vr+Vy+Vb=0 n under unbalance cond not equal to
zero.so that some current fkow through sec of pt n relay
operates

that is ans

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