Comparison of heat transfer characteristics between natural ester oil and mineral oil in large oil-immersed transformer

Natural ester insulating oil has the advantages of environmental protection and high ignition point. FR3 is a natural ester insulating oil that can be used in high voltage transformers above 110 kV. In order to provide theoretical guidance for the application of FR3 insulating oil in transformer. The heat transfer performance of transformer with FR3 insulating oil is evaluated by means of experiment and numerical simulation. In this paper, a heat transfer model of large oil immersed transformer winding is established and verified. The experimental results show that the accuracy of the established heat transfer model can reach 98.5%. The heat transfer performance of FR3 and traditional mineral oil are compared and analyzed by using the established heat transfer model. Research results show that: In ODAF cooling mode, the heat transfer performance of natural ester insulating oil is stronger than that of mineral oil;When the inlet temperature or low rate of the model is increased, the heat transfer advantage of natural ester insulating oil will be reduced; With the increase of coil heat load, natural ester insulating oil shows a better cooling performance; Especially in the area close to the guide plate, the heat transfer advantage of natural ester insulating oil become more obvious.