The most commonly used relay, for the protection of an alternator against loss of excitation, is

Answer :

Solution :

• Buchholz’s relay is used for the protection of transformer
• Differential relay is used for alternator winding protection
• Over-current relay is used for location where there is a chance of high current during fault
• Offset mho relay is used for the protection of an alternator against loss of excitation.

Hence, the correct option is (B).