Simulation Study Of Stray Loss And Temperature Rise In Ascending Flange Components Of Power Transformer

With the ever increasing of grid scale and generator capacity,the capacity and voltage level of power transformer has been improved continuously.So the structure of transformer is becoming more and more complex.Local overheat of metal structural parts such as tank and ascending flange caused by the leakage magnetic field has been paid more and more attention by the transformer production and operation department.In this paper,the problem of stray loss and temperature rise in ascending flange components of power transformer which caused by the leakage magnetic field of large current leads is studied.Taking an experimental model of the typical power transformer ascending flange as the research,the stray loss and temperature rise in ascending flange components of power transformer are systematically simulated and researched,and the heat source and overheat position are obtained,and the factors affecting stray loss and temperature rise are analyzed in the paper.It plays an important role in the design,optimization and safe operation of power transformers.Firstly,in order to solve the skin effect in the 3D stray loss calculation of steel plate,the surface impedance method and hierarchical method are adopted in the numerical calculation of TEAM Problem 21 with software MagNet.And comparing the results with experiment data,the surface impedance method is more efficient and reliable than the hierarchical method in the 3D stray loss calculation of magnetic steel plate structure of the transformer,which provides the basis for the analysis of complex engineering problems of large transformers.Secondly,the 3D simplified model of the experimental model of typical large transformer ascending flange is established with software MagNet,and the leakage magnetic field and stray loss are carried out by using the surface impedance method.The accuracy of the result is verified by comparing with the experimental values.And then the distribution of leakage magnetic field and stray loss of the ascending flange and tank cover is analyzed in different cases of current,material and electric shielding.The research provides the basic data for the design,optimization and temperature rise calculation of transformer ascending flange parts.Finally,combining the basic theory of heat transfer and experimental measurement data,the surface heat transfer coefficient and surface temperature conditions are got.On this base,the thermal field is calculated by the electromagnetic-thermal coupling method with the software ThermNet,and the result is in conformity with the measured value.The thesis also discusses the thermal field distribution in different conditions of current,material and electric shielding.And the application conclusions of product design are obtained.