Theoretical and Empirical-Based Thermal Modelling of Power Transformers

In the current study, we present an accurate approach for matching the calculated thermal performance of power transformers with measurements. It is done by adapting some well-known and used assumptions for building a theoretical thermal model based on special measurements for the objective of minimum deviation (±3 K). This can guarantee to meet specified temperature rises while providing an optimized high economical cooling system. The theoretical model calculated oil temperature distribution in medium power transformers. The model handles different winding designs and arrangements and solves for multilayer top-oil temperatures in a matrix form. It also calculates the temperature distribution in radiators, which can easily be validated during temperature rise test. First, the winding temperature is calculated, then the measured data from coolingcurves of a set of different transformer designs is inserted in the model. This implies correcting the calculated gradient and recalculating the top-oil temperatures. The model however is under development and in validation with a set of new manufactured transformers in parallel.