Temperature distribution in ONAN power transformer windings with finite element method

Abstract

Since large power transformers belong to the most valuable assets in electrical power networks, it is suitable to pay higher attention to these operating resources. Thermal impact leads not only to long-term oil/paper-insulation degradation; it is also a limiting factor for the transformer operation. Therefore, the knowledge of the temperature, especially the hot-spot temperature (HST), is of high interest. The calculation of current thermal stress helps to avoid unexpected outages. This paper presents the temperature distribution in windings of the oil power transformers. In this paper, energy (thermal) equation is solved until temperature is obtained. Oil in the transformer is assumed nearly incompressible and oil parameters such as thermal conductivity, special heat, viscosity, and density vary with temperature. For numerical solution of above equation, finite element method is used. The selected models for simulation are 300 KVA and 22.5 MVA ONAN transformers. Copyright © 2008 John Wiley & Sons, Ltd.