Research On Vibration Characteristics Of Power Transformer Considering Magnetostrictive Effects

In recent years China has increased in economic prosperity and the development of power industry is steadily advancing.With the continuous advance of the construction of power grid,voltage level and capacity of power transformer are increasing in the last decade.Vibration and noise are two intrinsic properties of the transformer in the process of electrical energy transformation.At the same time,vibration and noise are two significant characteristics that evaluate the quality of power transformer.On the one hand,the structural elements are apt to get loose because of vibration,and vibration might also destroy the internal insulation and decrease the operational reliability and economy of the system;on the other hand,the noise affect physical and mental health of the residents around.In this thesis,analysis on the core vibration of a small-scale single phase isolation transformer and a distribution transformer is given based on the mechanism of vibration.And this thesis is devoted to the research of vibration characteristics of transformer core which is under operating condition.The main contents of this thesis are listed as follows:(1)The vibration mechanism is studied and the vibration process of transformer core which is the transformer's major vibration source is studied.Based on the stressing feature of silicon steel sheet considering magnetostrictive effects,the column and yoke of transformer core are equivalent to elastic rod for analysis of forces.And vibration equations are derived which serve as a theoretical underpinning for the modeling in the future.(2)On the basis of vibration equations of transformer core,this thesis build the multi-physics coupled model to show the coupling relationship between electromagnetic field and force field.At the same time,the boundary conditions are given.(3)Grounded on the work above,a multi-physics coupled model for a small-scale single phase isolation transformer is built by using the finite element calculation software COMSOL.Vibration characteristics of transformer core are analyzed under different working conditions such as voltage excursion and frequency excursion.Finally the change rules of stress distribution and displacement distribution of a small-scale single phase isolation transformer are obtained.(4)A multi-physics coupled model which use the finite element method is also built to analyze the vibration characteristics of a power transformer in distribution network.Simulation results are given to show the change laws of core vibration under various working conditions which include different amplitude,frequency and harmonic components of exciting power supply.The results also show stress and loss of mass element of transformer core under different working conditions which include different column of transformer core.The research of the vibration characteristics of transformer core under different working conditions has some theoretical significance and practical value.Furthermore,it also provide a quite reliable theoretical foundation for the design and optimization of vibration damping and noise reduction of power transformer.