Electromagnetic-vibration Characteristics Of Y/△ Transformer With Inter-turn Fault

With the rapid development of China’s economy and the rapid improvement of social productivity,the voltage level and power grid capacity are increasing.As one of the core equipment in power system,transformer plays an important role in voltage conversion and power distribution.Whether it can operate stably or not is related to the security and stability of the whole power grid.The inter-turn fault between windings is one of the common internal faults of transformer.The aging and damage of insulation between windings is the main cause of inter-turn fault.The inter-turn fault of transformer is often accompanied by the increase of current,magnetic flux leakage and vibration of core and winding.If the transformer continues to operate in this state,it may cause the equipment to burn down or even the entire power grid to collapse.Based on the National Natural Science Foundation Project(51507027),Jilin Science and technology innovation development plan project(20166014),Jilin Science and technology development plan project(20190303007SF),the electromagnetic characteristics and vibration law of Y/A transformer with inter-turn fault at different positions are studied.Firstly,this paper introduces the calculation principle of edge finite element method,and verifies the accuracy and effectiveness of edge finite element method in solving magnetic field problems through simulation.Secondly,the single-phase transformer is taken as an example to establish the electromagnetic coupling model.The dynamic inductance is obtained through the magnetic field model.The time-domain current is obtained based on the circuit model.The dynamic inductance and time-domain current are used as the key parameters to realize the electromagnetic coupling through cyclic iteration,and the simulation results show that the model can effectively simulate the electromagnetic characteristics of the transformer.On this basis,the state equation of Y/A transformer with inter-turn fault is constructed,the magnetic field model and circuit model are solved by energy balance finite element method and improved Euler method respectively,and the distribution of port current,short-circuit turn current and leakage flux of transformer with inter-turn fault at different positions are simulated and analyzed.At the same time,the dynamic model test platform of Y/A transformer with inter-turn fault at different positions is built,and the waveforms of port current and short circuit turn current are recorded by oscilloscope.The feasibility and validity of the Y/△ transformer electromagnetic coupling model are verified by comparing the simulation results with the experimental data.Aiming at the problem of winding vibration aggravation caused by inter-turn fault of transformer,an electromagnetic-vibration harmonic response model is proposed on the basis of electromagnetic coupling,and the corresponding relationship between electromagnetic characteristics and vibration of windings with inter-turn fault at different positions is studied.The vibration characteristics of windings with inter-turn fault at different positions are simulated and summarized.The dynamic model test platform of Y/△ transformer with inter-turn fault at different positions is built to monitor the vibration of t windings on line.The correctness of the conclusions is verified by comparing the simulation results with the experimental data.