To prevent mal-operation of differentially connected relay while energizing a transformer, the relay

To prevent mal-operation of differentially connected relay while energizing a transformer, the relay restraining coil is based with 

(1) second harmonic current 

(2) third harmonic current 

(3) fifth harmonic current 

(4) seventh harmonic current
by

1 Answer

Answer :

To prevent mal-operation of differentially connected relay while energizing a transformer, the relay restraining coil is based with  second harmonic current 

by

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