Simulation Study On Strength Of Winding And Supporting Structure Of Power Transformer Under Short Circuit Condition

With the continuous development of the energy Internet,power transformers play an increasingly important role in the power system.The strength of the winding and its supporting structure in the short circuit state of the power transformer is analyzed,and then the tolerance of the short circuit force of the transformer is accurately evaluated,which can provide a powerful reference for the verification of the mechanical strength and operation and maintenance of the power transformer.In order to make the simulation analysis closer to the real situation,a fine winding model of a three-phase five-column transformer is established to simulate the real winding structure,and the deformation of the winding after the power transformer is impacted by a short circuit is analyzed and evaluated.Firstly,in order to study the difference between the three-phase short circuit at the transformer outlet when the A-phase voltage crosses zero and the B-phase voltage crosses zero,a common transformer model for electromagnetic calculation is established in this thesis,and the Maxwell transient field solver is used to solve the short-circuit current changes in these two short circuit states.The magnitude and distribution law of both the magnetic flux leakage in the space where the winding is located and the short circuit electromotive force received by the winding when the impulse short circuit current occurs are calculated,and based on this,the most severe short circuit impact is selected for further analysis.Uses the ANSYS APDL command flow to build a detailed model of the transformer winding with a real winding structure.The winding model includes low-voltage helical windings,high-voltage and medium-voltage continuous windings,and considers the S-bend of the inter-turn transposition of the windings.In order to select a suitable support structure,this thesis takes three-cake windings in consideration of the elastic-plastic deformation of the material according to the characteristics of the transformer winding and its support structure.Under the condition of fixed load,the influence of the number of spacers,the width and whether the wedge spacer is added at the S-bend on the axial strength of the winding is studied respectively,and the effects of the number and width of stays on the radial strength of the winding.Finally,in the ANSYS Workbench software,the method of "electromagnetic-structural " coupling is used to study the stress and deformation distribution of the winding under a single short circuit impact and the short circuit impact tolerance of the winding.At the same time,the law of winding deformation under multiple short circuit impact is studied,and the stability of winding and its supporting structure after multiple short circuit impact is judged by B-R criterion.