Identification of Various Internal Faults of Transformer Based on No-load Current Analysis

Abstract

The internal faults of transformer can be identified by various techniques. The proposed technique is by the analysis of no-load current and harmonic contents present in it. The no-load current of transformer is non-sinusoidal for sinusoidal input voltage. And hence it contains harmonics in healthy condition of transformer. But if transformer has any internal fault then the no-load current magnitude and its harmonic content will vary depending upon the type of fault. The winding fault increases the %THDi and magnitude of no-load current, whereas the core fault increases only the %THDi of no-load current. For winding fault if the inter-turn fault is on the primary side then both %THDi and magnitude of no-load current increases but if the inter-turn fault is on secondary side then only magnitude of no-load current will increase.