Analysis Of Inter-Turn Short Circuit In Transformer Winding Based On The Electromagnetic Coupling

The normal power transformer winding may occurs short-circuit in the case of insulation damage.At the same time,the short-circuit current,the distribution of magnetic field,the force and the vibration of windings are related to the safety and reliability of the transformer and even the whole power network.This paper is combined with the project funded by the National Natural Science Foundation of China(51507027),Jilin Science and Technology Innovation and Development Project(20166014)and Jilin Science and Technology Innovation and Development Project(20190303007SF).The study is focus on the simulation model,magnetic field and current characteristics,and electric characteristics in inter-turn short circuit of transformer winding.Firstly,the computational advantages of the edge finite element method for electromagnetic field is introduced.The calculation principle of the edge finite element method is given in this paper.Then,the time-domain electromagnetic coupling model with dynamic inductance and time-domain current as key coupling parameters is proposed.The transformer simulation model is built based on this mechanism.It can not only reflect the excitation state of the transformer,but also can easily calculate the winding force distribution.At the same time,the electromagnetic field simulation calculation model of the transformer winding turn-to-turn short circuit is built,and the meshing and pre-processing operations of the simulation model are completed by the finite element method.Finally,the characteristics of the leakage magnetic field distribution about the normal transformer are analyzed.The voltage regulation tapping area in the high voltage winding and the uneven longitudinal insulation along the axial height,may cause ampere-turns disequilibrium along the axial winding.The characteristics of the leakage magnetic field distribution are discussed.Three-dimensional finite element model of single-phase transformer is built based on the field-circuit coupled theory in this paper,and the transformer inter-turn short circuit problem is researched in no-load operation.By analyzing the winding current,flux and force as inter-turn short circuit appears in different positions,the relationship between the transformer excitation and the winding force is studied.And the changing regulation is summarized.On this basis,numerical simulation and physical test are carried out.The vibration acceleration of short circuit winding is simulated and measured.Comparing the simulation results with experimental data shows correctness and effectiveness of the method.