To prevent mal operation of differentially connected relay while energising a transformer, the relay restraining coil is biased with
A)Second harmonic current
B)Third harmonic current
C)Fifth harmonic current
D)Seventh harmonic current

Question

Quizplus · Accepted Answer

Second harmonic currents are used to bias the restraining coil of a differentially connected relay during the energization of a transformer to prevent maloperation. This is because the inrush current, which occurs during transformer energization, contains a high level of second harmonic components, distinguishing it from fault currents.

To Prevent Mal Operation of Differentially Connected Relay While Energising