Transformer incipient inter-turn fault detection based on no-load current harmonic analysis

This paper presents use of no-load current harmonic analysis to detect presence of inter-turn fault at incipient stage. At steady state, third and fifth harmonic components are predominant in transformer no-load current. Inception of fault results in decrease in THD and increase in increase in primary current. Based on reduction of total harmonic distortion (THD) of each phase and simultaneous increase in primary current, it is possible do detect presence of inter-turn fault. Wavelet analysis is also performed to validate the results. Proposed method offers higher sensitivity and accuracy as it can detect fault at incipient stage involving less than 2% turns and fault current up-to 1 p.u.