The Research On Resistance Characteristics And Structural Improvement Of Transformer With Vertical Oil Channel

With the development of the electric power industry,the rated capacity of transformers has continuously increased.The temperature rising problem of transformer has become the focus of research.In this paper,the flow field and temperature field of transformer windings and external cooling system are analyzed by CFD method for a large oil-immersed transformer,meanwhile,the oil flow distribution of the internal channel is investigated.Based on this,a series of improvement researches are carried out.The result provides an advanced reference for the industrial applications.Firstly,a three-dimensional axisymmetric model of the low-voltage winding for transformer is established to analyze the flow field and temperature field distribution.The structure of the low-voltage winding is improved in the horizontal low-velocity zone near the oil inlet and in the high-temperature concentration zone near the outlet.The results show that the winding temperature decreases with the increasing of horizontal spacing.Increasing the horizontal spacing between 10 th and 13 th layer winding can reduce the hot spot temperature by 2.21°C.This scheme presents the best improvement effect.In addition,the structural improvement is based on the size of the axial flow channel.The results show that the hot spot temperature decreases with the increasing of axial dimension.When the axial dimension is 10 mm,the hot spot temperature drops by 2.5°C.Based on the axial dimension improvement results,the influence of the number of guide zones on the winding temperature field is explored.The results show that the improvement effect of setting three guides in 4 section winding respectively is the most obvious.The average temperature of the windings is 2.41°C lower than the prototype,and the hot spot temperature is decreased by 1.77°C.Secondly,a three-dimensional axisymmetric model is established for the medium voltage winding to analyze the flow field and temperature field distribution.The influence of the axial dimension on the temperature field is investigated.The results show that the hot spot temperature increases with the increasing of the axial dimension.Based on the improvement of the axial,the influence of the guide zones on the temperature field of the winding is investigated.It is found that the average winding temperature decreased with the increasing of the guide zone number,but the hot spot location rule is not obvious.When the guide zone number is more than 3,the hot spot temperature increases with the number of guide zones,but the increase tends to be gentle.Finally,for the radiator,the heat transfer performance of four groups of radiator is studied under three cooling modes,namely natural convection,horizontal blowing and vertical blowing cooling modes.The heat dissipation and the average convection heat transfer coefficient for horizontal blowing cooling and vertical blowing cooling modes are compared and analyzed.In terms of heat dissipation,the former is 0.5% higher than the latter;In terms of average convection heat transfer coefficient,the former is about 11% higher than the latter,The reason is that more air gets wasted from the sides for vertical blowing cooling modes.Based on the results of the natural convection heat transfer for four sets of radiators,the effects of height,number of fin,and spacing on the heat dissipation performance are explored.It is found that on the basis of the original model,reducing the height,decreasing the number,and reducing the plate spacing are beneficial to the heat transfer.