Impact in Substation Power Transformer Due to Injection of Non-linear Load

Abstract

In electrical power system transformer is consider as one of the mostly used major component. The thermal condition of transformer is considered as a critical case while operating in abnormal conditions such as harmonic loading is the main focus of the study. In this thesis, 22.5 MVA, 66/11 kV, ONAF power transformer thermal behavior analysis is carried by using IEEE standard C57.91 model for the study of influence due to nonlinear load and impact on its life which is simulated by using MATLAB software and analyzed. The transformer considered in the study shows the significant life reduction while non-linear loads is injected above 15% of the transformer capacity rating for both winter and summer season. It concluded that higher the harmonic load current there will be additional losses towards transformer windings along with core which cause raise in temperature of transformer higher than the standard operating temperature. This indicates that hot spot temperature increases by 2⁰C for every 1% increase of non-linear loading of rated capacity of transformer along with 2% increase in size of transformer for the case of winter whereas the increase in temperature is 2.7⁰C and size increase by 3% in case of summer.