100MVA Non-Uniform Heat Losses Study

Abstract

Through the use of a computational fluid dynamics method, a two-dimensional axisymmetric thermal analysis was performed focusing on the layered low-voltage winding of a 100MVA power transformer. After the previous study that offers the thermal losses of each disk, a comparison is sought to observe the results with uniform and non-uniform distributions of these losses along the entire section taking into account the unbalance caused by the appearance of eddy currents in parallel conductors. The results were applied to two cases: mineral oil and synthetic ester considering ONAN regime for the axial cooling system which, presents two inlet and two outlet mass-flows. For each of the precisely compared cases, the hot-spot temperature and its localization for different eddy current loss coefficients were calculated, revealing that the use of mineral oil results in a larger mass flow rate in the channel and a smaller hot-spot temperature. Moreover, a higher accuracy in the values of this parameter and its location have been found in the non-uniform losses case.