Dynamic thermal modelling of power transformers

Summary form only given. The aim of This work is to introduce hot-spot and top-oil temperature thermal models for more accurate temperature calculations during transient states, based on data received in a normal heat run test (i.e. the top oil in the tank of transformer and the average winding-to-average oil gradient). Oil viscosity changes and loss variation with temperature are taken into account. The new thermal models will be validated using experimental (fiber optic test) results obtained at varying load current on a 250 MVA-ONAF-cooled unit, a 400 MVA-ONAF-cooled unit and a 605 MVA-OFAF-cooled unit. The results are also compared with the IEEE-loading guide (1995) Annex G method.