The Analysis Of Radial Electrodynamics Force And Stability For Large Power Transformer Windings

Power transformers The transformer is an indispensable key component in the power system,it can not only transmit and distribute electrical energy and also transform the voltage level of the transmission and distribution lines,the function and position of transformer in the modern power system is self-evident.In recent years,UHV power grid has developed rapidly,and the requirements for transformer stability are also increasing.If the transformer occurs the short circuit fault under the UHV voltage level,the electric force on its windings will rapidly increase to tens times until nearly a hundred times,the problem of radial stability has been attracting more and more attention of scholars and experts all over the world,the stability of transformer windings has become one of the urgent need to study and solve the issue of electric power industry.This paper focuses on the study of a double winding transformer of 120MVA/ 220 k V,taking Mag Net finite element software as platform,the method based on Field Circuit Coupling,establishing a simulation model of three-phase symmetrical short circuit transformer.In order to make the model accurate,we had verified by the method of harmonic and obtained the time and space distributions of leakage flux and radial short-circuit force of high and low voltage windings on this basis.The radial stability analysis of the transformer winding is closely related to the inward compression and outward stretching of the internal and external pressure windings under the action of radial short-circuit electric force.The radial stability of low voltage winding is evaluated by linear buckling analysis.On the basis of considering the dynamic characteristics of the winding,the winding structure and the unequal force,the critical load that can be carried by a low-voltage winding is determined,and find the safety margin of the cake that the low voltage winding line can withstand.In combination with the linear buckling analysis process and results,in order to make the solution more accurate and the simulation more in line with the actual situation,the nonlinear solver is restarted to obtain the radial critical displacement value of the wire cake.Finally,the critical buckling displacement of the winding can be solved by the formula,and then the whole process of the stability verification of the low voltage winding is completed.For the radial stability analysis of high voltage winding,the radial strength and radial displacement are used as the basis for evaluation.Firstly,based on the basic mechanics principle,the three-dimensional cylindrical solid model of the winding cake is established by using the ANSYS finite element software.When the radial short-circuit force of each wire cake is applied to the corresponding line cake,the transient solver is started,and the radial displacement deformation is solved when the wire cakes are loaded by cyclic loading.After the research of winding stability,it is proved that the winding stability of an example transformer is better under the excitation of short-circuit electric power in the high and low voltage windings.At the same time of correlation calculation and analysis,the research has also provided practical reference for the future domestic and foreign experts and scholars on the transformer winding stability of the relevant research topics.