Research On The Thermal Resistance Characteristics Of Oil-immersed Transformer Windings Wrapped With Insulating Paper

In order to ensure the safe and stable operation of the national grid,the hot spot temperature of the large oil immersed power transformer should be kept in the safe amplitude for a long time.Because of the complexity of the internal structure o f the transformer,the uneven temperature distribution inside the system will cause the performance of the insulation system to decrease,and threaten the service life and saf e operation of the transformer.Establishing and optimizing the thermal model of transformer temperature field is an important way to analyze the hot spot temperature of transformer winding at present.Define the thermal resistance parameter of insulation paper of oil immersed transformer is the key to perfect the model and improve the accuracy of the model.The main contents of this paper are as follows:(1)According to the special properties and structural requirements of the research object,the experimental method and numerical simulation theory of thermal resistance applied to transformer winding outsourcing insulation paper were investigated and analyzed,and the experimental principle and calculation model were selected and improved to make it suitable for this research.(2)According to the contact condition of insulation paper,improved the numerical model of thermal contact resistance,analyze the surface topography of insulation paper and copper by atomic force microscopy,obtain the number of convex peaks,degree of heat flux shrinkage and other parameters of surface morpholo gy.Finally calculate the thermal contact resistance between insulation paper and copper.(3)Design the experiment device based on the steady double heat flux meters method,the improved experimental model can be used for the separation of contact resistance and body resistance,Select material and treated it,assemble the experimental device and make reasonable experimental steps,the experimental research on the thermal resistance of the insulat ion paper is completed(4)By processing the experimental dat a,obtained the curve of the thermal conductivity and the contact thermal resistance with the temperature of the insulating paper under different working conditions.At 70 degrees,the experimental value of thermal contact resistance between copper and oil immersed insulation paper is0.000575m~2k/w,and the calculated value of contact thermal resistance is0.000541m~2k/w.The experimental value of thermal contact resistance between copper and insulation paper is 0.0026m~2k/w,and the calculated value of conta ct thermal resistance is 0.00231m~2k/w.With the increase of experimental temperature,the thermal conductivity of insulation paper decreases and the contact thermal resistance increases.Comparing the experimental data with the calculated data,they are in good consistency.The research can provide data support for the establishment of the thermal circuit model,and has a good application prospect.In this paper,the thermal resistance characteristics of transformer winding insulation paper are studied thr ough theoretical analysis and practical experiments.Following works has been done in this paper:the micro surface morphology of insulating paper and copper is described,t he numerical model of contact thermal resistance and numerical calculation of conta ct thermal resistance are established.the experimental principle,determined the experimental device,processed and analyzed the experimental data.The above experiences have great reference values to establish the thermal model of transformer temperature field.