| As the main operation and protection device in electric power grid,vacuum switches.including vacuum circuit breakers,vacuum load switches and vacuum contactors,have the advantages of strong arc extinguishing ability,short arcing time,small wear of electrical contacts and long electric life.Its interrupting performance has a direct impact on the safe operation of the power grid.The vacuum switch is used to cut off large short-circuit current through the extinction of vacuum arc.The morphological characteristic of vacuum arc has an important influence on the interrupting performance of vacuum switch.The vacuum arc is in a vacuum environment and the medium is metal vapor,and it is influenced by various electromagnetic factors,which has a rich and complex subtle.morphological features.Although there may contain certain rules,but it is difficult to express with simple mathematical formula.In the current interruption process,agglomeration arc prone,causing surface ablation,craters,and even lead to the failure of contact,resulting in the breaking failure.Introducing appropriate longitudinal magnetic field can effectively avoid the appearance of agglomeration arc.The researches on the morphology of high current vacuum arc,the vacuum arc shape control through magnetic field and the influences of high current vacuum arc to the heat issue problem of vacuum cabinet are very important in improving the interrupting capability and reliability of vacuum circuit breaker.The main contents are as follows:The characteristics of large current arc morphology of short gap high current vacuum arc is studied.A data acquisition system of vacuum switch arc is set up according to the vacuum arc generation mechanism.The main circuit,trigger circuit and freewheeling circuit of the vacuum arc experiment are designed,and the high-speed image acquisition of the vacuum arc process is carried out by using CMOS sensor.In order to study the morphological detail characteristics of high current vacuum arc better,using digital image processing technology,the traditional arc detection,mathematical morphology edge detection and wavelet multi-scale edge detection method are used to compare and analyzes the arc shape detection.Based on the wavelet multi-scale edge detection method,the morphological changes and characteristics of the combustion process of vacuum arc are studied.By using the microscope and multi-scale property of wavelet transform,the detail characteristics of vacuum arc morphology are studied,and a new multi-scale morphological edge thinning detection algorithm is proposed.In order to promote the application of vacuum switch in the high current field,it is necessary to carry out the design and analysis of high current vacuum arc chamber in combination with the characteristic of high current arc.The ANSOFT software is used to simulate and analyze the electric field intensity in the vacuum interrupter under different shielding structure,contact thickness and contact opening distance,and the three-dimensional magnetic field of the vacuum interrupter is studied.Based on the results of electromagnetic simulation,a new cylindrical core structure of vacuum interrupter is designed.The magnetic intensity is simulated as the slot number and structures are different.The new type of high current vacuum interrupter can enhance the longitudinal magnetic field of vacuum interrupter and improve the control ability of vacuum arc morphology.In the process of the high current vacuum arc extinguishing chamber,the heat dissipation condition and temperature rise of vacuum switch cabinet are also one of the important research subjects in this field.Based on the CFD simulation software Fluent,the temperature rise and heat dissipation of the large current switch cabinet are studied by simulation.The 3D model of double bus switch cabinet is built by GAMBIT,and the meshing and setting boundary conditions and temperature field simulation are analyzed.The full closed,natural ventilation and forced ventilation system programs were carried out to simulate temperature field,the maximum temperature are influenced by.the wind velocity,air inlet position,the heating power.Based on the temperature field simulation of high current vacuum cabinet,the relationship between the temperature rise and the heat dissipation mode is obtained. |
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