Estimation of hot spot temperature in distribution transformer considering core design using FEM

Power transformers represent the largest portion of capital investment in transmission and distribution substations. One of the most important parameters governing a transformerpsilas life expectancy is the hot-spot temperature. Therefore design of transformer is so important that should be considered. Core is one of parts of transformer that is effective on hot-spot temperature. This paper presents a methodology to assess the effect of various designs of transformer core and operating parameters on the hot spot and top oil temperature in 3oslash Core type distribution transformer. In order to estimate the temperature, first losses in transformer is evaluated by finite element method (FEM), and then the hot spot and top oil temperature are calculated using a thermal model of a distribution transformer. Last, the transformer efficiency according to the variation of daily load and core dimensions is discussed.