Negative sequence based relay operate area approach to detect transformer inter-turn fault

This article presents a new approach for transformer inter-turn fault detection. Conventional differential scheme is provided with bias to prevent mal-operation in case of over-excitation, CT saturation, magnetising inrush, etc. However, this prevents conventional scheme from detecting inter-turn fault at incipient stage where less turns are involved in the fault. Proposed scheme overcomes this drawback by introducing Relay Operate Area (ROA) approach. The proposed two stage approach initially detects presence of fault and later confirms the presence for observation based on predefined loading conditions. Experimental results on laboratory transformer are presented which confirms the proposed approach.