Numerical simulation of temperature field of converter transformer based on electromagnetic-flow-heat coupling field

The converter transformer plays a key role in the safe operation of power system. Due its high voltage level and complex heat transfer characteristics, the heating problem becomes the important problem affecting the safe and stable operation of converter transformer. With a 500Kv oil-immersed converter transformer as research object in this study, the distribution of magnetic flux leakage, eddy current loss and temperature field were calculated by three dimensional electromagnetic-flow-thermal coupling field analysis method, considering the effects of conduction, convection and radiation on the heat transfer of structures. The results showed that the magnetic flux leakage distribution was symmetrical. The transverse distribution was characterized by small leakage magnetic flux in the middle, while large leakage magnetic flux at both ends. The longitudinal distribution was characterized by small leakage magnetic flux at both ends, while large leakage magnetic flux in the middle. The eddy current loss had a great influence on the middle of the winding while little influence on the both ends. For the same position, the temperature of the valve winding was lower than that of the net winding. The position of the highest temperature point inside of iron core was within the range of 70%similar to 90% of the total height. This study provides certain theoretical basis for the study of long-term stable operation of transformer.