TRANSFORMER FAULT DIAGNOSIS BASED ON HARMONIC ANALYSIS OF NO-LOAD CURRENT

Abstract

Aim: To diagnose the winding and core fault in transformer from no-load current analysis. Methodology: This paper deals with diagnostic method of the internal fault of transformers. The current diagnosis methods (e.g. oil test, dissolved gas analysis (DGA), partial discharge (PD) etc.) have some merits and demerits. The proposed technique to diagnose the fault in transformer is from the knowledge of transformer’s no-load current and its harmonic contents. The no-load current of transformer is non-sinusoidal for sinusoidal supply voltage. The harmonic content in no-load current varies for healthy and faulty transformer. The proposed technique uses the data obtained from the no-load harmonic test on transformer as per IS-2026-16.3. Results: In this paper it is shown that for winding fault the no-load current magnitude and %THD in no-load current increases significantly, where as for core damages the only %THD of no-load current increases. Conclusion: From the knowledge of no-load current and its harmonic contents the winding fault,
core material quality and core fault can be easily identified. Hence, by measuring no-load current the possible fault can easily be diagnosed.