Protective relays are devices that detect abnormal conditions in electrical circuits by measuring
Right Answer is:
Constantly the electrical quantities which differ during normal and abnormal conditions
A relay is an automatic electric device used to initiate the isolation of a part of a circuit. A relay (automatic device) used for the protection of a circuit during abnormal conditions is called a protective relay. Protective relays require reasonably accurate reproduction of the normal and abnormal conditions in the power system for correct sensing and operation.