Core Magnetization Effect in Sweep Frequency Response Analysis for Transformer Diagnosis

Power transformer is one of the most prominent equipment in the area of power sector. Increasing power demand at world level requires manufacturing of large number of oil immersed power transformer. With increase in size and MVA rating of power transformer, the chances of failure also increases simultaneously. Cost of replacement of whole transformer is much more enough compared to regular condition monitoring of transformer. In this paper, efforts are made to analyse the core magnetization effects in low frequency range for high voltage, low voltage and tertiary voltage winding. In low frequency range, core magnetization inductance is dominant over winding inductance and hence responsible for magnetization effect. There is lot of irregularities for resonance amplitude at resonance frequency for SFRA signature, which indicates core magnetization effect. A case study has been presented in this paper for 315 MVA rating transformer through design based interpretation techniques.