Electromagnetic and thermal modelling for prognosis of distribution transformer

Abstract

In this thesis numerical modelling of electromagnetics and thermodynamic of a distribution transformer was studied. The model is based on two 5 MVA three phase distribution transformers located in Uleberg (Norway) owned by Agder Energi. The results include magnetic flux density in the core, current density, heat loss density and temperature distribution in the transformer. The maximum temperature of the transformer operating at full load with cooling fans turned on and ambient temperature 20 C, reached the expected value based on temperature measurements from the transformers in Uleberg provided by Agder Energi. The results of the transformer operating at these condition were as a reference for the other simulations. The transformer model was simulated at different ambient temperatures and when the cooling fans were turned off. The effect of heat transfer by radiation and uniform current density were also investigated. The results of temperature of different operating condition were used to prognose the ageing rate of the transformer's paper insulation. The measurement data provided by Agder Energi was processed in Excel, and the numerical modelling was executed in Comsol Multyphysics. .