Detection of Interdisc Faults in the Windings of Power Transformer

In extra high voltage power transmission, power transformer is the most important component. Insulation failure within transformer is considered to be one of the most important causes of failure of power transformer. Comparison of neutral currents at reduced and full voltages was carried out for detection of fault in a power transformer winding during impulse test. In order to assess the integrity of the winding, high voltage power transformers were subjected to full and chopped impulse voltages of specified values in accordance with the standard requirement. One of the tests carried out was the comparison of applied voltage and resultant neutral current signal at reduced and full voltage levels. The difference in wave shape of the recorded current and voltage signal confirmed the existence of fault in the transformer winding. In the present work, 61MVA, 11.5/230 kV generator transformer has been considered for analysis. The component of the noise which is inherent in the signal during recording was isolated using Daubechies wavelet and these de-noised signals were analyzed to identify the fault in the winding.