Multi-physical Field Coupling Simulation Analysis Of Nano Oil Transformer

Since the 21st century,China’s economy has entered the track of rapid development.At the same time,the demand for electricity of our people is also growing rapidly.In this context,it is particularly important to further build and develop UHV transmission network.UHV transmission network can meet the urgent demand for power in China.In power grid construction,oil-immersed transformer,as one of the main transmission and transformation equipment,is widely used and plays an important role.With the increase of transformer capacity and transmission voltage level,in order to ensure the safe and stable operation of transformer,the problems of transformer insulation and heat dissipation must be fully considered.The rise of nanofluids has brought new opportunities to the development of transformer industry.Nanofluids are very popular in energy,industry and other industries because of their good thermal conductivity.The nano-particles are dispersed into ordinary transformer oil by a certain method.The nano-modified transformer oil can improve the heat dissipation performance of transformer and solve the problem of local overheating of transformer.The application of nano-modified transformer oil can promote the development of transformer toward the direction of large capacity,small volume and low cost.In this paper,Al₂O₃nano-modified transformer oils with different volume fractions were prepared,and the related aspects of thermal conductivity were studied.The results show that the thermal conductivity of Al₂O₃nano-modified transformer oil is higher than that of ordinary transformer oil in varying degrees,and the relationship between thermal conductivity of nano-modified transformer oil and temperature and nano-particle concentration is obtained.In this paper,a three-phase two-winding oil-immersed self-cooling transformer with rated capacity of 400 k VA and rated voltage of 10 k V is analyzed.According to the structure characteristics and main technical parameters of the transformer,the transformer is simplified and assumed rationally,and the simplified model of the transformer is established.A simulation platform of transformer electromagnetic-temperature-fluid multi-physical field coupling is built by Workbench software.Firstly,finite element simulation software is used to solve the internal magnetic field of transformer.The electromagnetic field of transformer under no-load and short-circuit conditions is analyzed and the loss of transformer is obtained.Secondly,the transformer loss solved by finite element simulation software is used as heat source by computational fluid dynamics software to solve the temperature-fluid field of transformer filled with ordinary transformer oil and Al₂O₃nanometer modified transformer oil.The temperature distribution and oil flow distribution in transformer filled with two different transformer oil are obtained.The results show that the inner temperature of transformer filled with Al₂O₃nanometer modified transformer oil is significantly lower than that filled with ordinary transformer oil,and the temperature rise of hot spot of the former winding is about 5.6K lower than that of the latter.In the process of practical engineering application and optimization design of oil-immersed power transformer,the simulation results in this paper can provide some reference for the designers of nano-transformer.