Answer / meenakshi

Differential relay is one that operates when the phasor
difference of two or more similar electrical quantities
exceed a predetermined value. Thus a current differential
relay is one that compares the current entering a section
of the system with current leaving the section.Under normal
operating conditions, the two currents are equal but as
soon as fault occurs, this condition no longer applies. The
difference between the incoming and outgoing currents is
arranged to flow through relay operating coil. If this
difference is equal to or grater than the pick up value the
relay will operate and open the circuit breaker and isolate
the faulty section.
mainly used in two winding transformers

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