Abstract
The winding hot-spot temperature is an extremely important factor limiting the loading capability of a power transformer. High temperature also accelerates the aging of paper insulation and thus reduces the lifetime of a transformer. Ohmic losses in the winding are the main source of heat inside a transformer. Precise knowledge of these losses is very important to determine the winding temperature distribution. Furthermore, in an oil-immersed power transformer, oil is used both as insulation and as liquid coolant. In a disc-type winding, a non-uniform coolant flow, in horizontal ducts, can contribute to local overheating. This article describes a new approach to estimate the winding temperature distribution, in which losses are computed by the finite element method whereas the coolant circulation and the temperature distribution are obtained from a thermal-hydraulic network representation of the winding. © 2012 IEEE