Temperature distribution in power transformer windings with NDOF and DOF cooling

Power transformers represent the largest portion of capital investment in transmission and distribution substations. In addition, power transformer outages have a considerable economic impact on the operation of an electrical network. One of the most important parameters governing a transformerpsilas life expectancy is the hot-spot temperature (HST) value. The classical approach has been to consider the hot-spot temperature as the sum of the ambient temperature, the top-oil temperature rise in tank, and the hot-spot-to-top-oil (in tank) temperature gradient. In this paper energy (thermal) equation is solved until temperature is obtained. For numerical solution of above equation, finite element method is used. The selected model for simulation is 32MVA transformer with non-directed oil-forced (NDOF) cooling and directed oil-forced (DOF) cooling.