Evaluation of The Performance of Different Relays under Magnetizing Inrush Current.(Dept.E)

Abstract

Harmonic restraint differential relays are popular in practice for transformer protection. Under magnetic inrush current, these relays should not operate since the harmonic restraint discriminates between this current and short-circuit current according to the harmonic analysis of the two waves. This analysis is carried-out for different operating and design parameters of the protected transformer. The resulted data is used to evaluate some practical differential relays with harmonic restraint. A new idea for a restraining feature of differential relay is of introduced.