| The safe operation of the power system is related to the lifeblood of the national economy and national energy security,and the power transformer,as an important part of the power system,needs to know its hot spot temperature,reduce its failure probability,and extend its service life.In this dissertation,due to the complex structure and large volume of the large oil-immersed power transformer,it is difficult to balance the degree of three-dimensional model reproduction by the numerical analysis method with the computational power demand of the computer.Taking an oil-immersed self-cooling power transformer as an example,this dissertation studies the influence of temperature on copper consumption and the influence of non-uniformity of loss distribution on temperature by using the field-circuit coupling method.The distribution law of the fluid field and temperature field of the transformer is obtained after several iterations.On this basis,the optimization measures for the winding structure are given.Firstly,considering the structural characteristics,cooling fluid flow path,and parameters of the transformer,the overall flow path model is established,and the three-dimensional numerical analysis model of the high and low voltage windings and radiator parts of the real insulation,bracing,and oil passage pad parameters is established.According to the heat transfer characteristics of an oil-immersed power transformer,the winding and heat sink are decoupled from the transformer by the transformer oil flow path.The flow path provides the inlet boundary conditions for the numerical analysis of the winding and the radiator.The flow resistance corresponding to the flow path is corrected by the numerical analysis model.The temperature distribution of the winding is accurately predicted by the two-way coupling of the flow path and the three-dimensional numerical analysis model,and computational resources are saved.Secondly,in the coupling solution of the winding local fluid field and temperature field,the original uniform distribution of copper consumption,the uniform distribution of copper consumption affected by temperature distribution,and the non-uniformity of copper consumption distribution were compared and analyzed in the heat source loading,and the transformer winding temperature distribution under three kinds of loss was obtained.Considering the effect of temperature on copper consumption and the non-uniformity of distribution,the calculated results are closer to the actual situation.Finally,the influences of fluid velocity,winding radial oil channel height,and the number of radial oil channels between oil baffle plates on hot spot temperature were analyzed.In order to simplify calculations,insulation,stays,and oil channel pads were simplified in the fluid field-temperature field model.Through the fluid field-temperature field coupling analysis,the relationship between hot spot temperature and velocity,radial oil channel height,and the number of radial oil channels between oil baffle plates was obtained.It was found that the velocity and hot spot temperature were negatively correlated,and the hot spot temperature was positively correlated with the radial oil channel height and the number of radial oil channels between oil baffle plates at the same velocity.It is studied that the lower radial oil passage is adopted in the upper part of the winding along the axial height,and the reduction of the number of oil baffles in the lower part can further reduce the hot spot temperature and improve the winding temperature distribution. |
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