Coupled CFD and electromagnetic analysis of an ONAN distribution transformer cooled with mineral oil and biodegradable esters

MELKA BARTLOMIEJ; PALACZ MICHAL; STEBEL MICHAL; BODYS JAKUB; HAIDA MICHAL; GARELLI LUCIANO; RIOS RODRIGUEZ GUSTAVO; STORTI MARIO; KUBICZEK KRZYSZTOF; LASEK PAWEL; STEPIEN MARIUSZ; PESSOLANI FRANCISCO; AMADEI MAURO; GRANATA DANIEL; SMOLKA JACEK

Kraków

Congreso; 6th International Conference on Contemporary Problems of Thermal Engineering; 2020

Silesian University of Technology and Department of Thermal Technology

Power losses accompany each electrical device during its work. The proper power losses dissipation to the ambient allows avoiding the device overheating and its operation failure. One of the most effective techniques for the cooling of internal parts of the electric devices, such as transformers, is the implementation of a dielectric coolant within the device casing. Nowadays, the most popular coolants in the market are based on mineral components. However, mineral oil is not neutral for the environment, especially in a case of coolant leakage or its disposal after the device lifetime. More environmentally friendly coolants belong to the liquid group of biodegradable oils where the most common representative is ester oil. For this reason, the main aim of this work was to compare the cooling efficiency of both coolant types in the 315 kVA distribution transformer at different ambient conditions. The developed coupled numerical model included both electromagnetic, thermal and flow phenomena. The power losses were interpolated into the Computational Fluid Dynamics (CFD) submodel as volumetric heat sources. Finally, the CFD model was used to determine hot-spot temperature within the transformer tank. The calculations were conducted for mineral and ester oils at different climate conditions that correspond to the conditions of central Argentina and Poland. The resulting hotspot temperature resultsobtained for the ester oil scenario were up to 3 K higher than that obtained for mineral oil case. Inaddition, the numerical results showed a satisfactory agreement with the measured values within the analyzed distribution transformer.