The Analyse About The Prebreakdown Characteristic In Dielectric Liquids Based On The Field Ionization Mechanism

Along with dielectrc liquids are used widely in power equipments, in recent years, electrical accidents resulted from liquid discharge is increasing year by year. So liquid discharge receive more and more attention of researchers. Therefore, the study of the mechanism behind the liquid discharge become significant to prevent liquid discharge or insulation aging, and to provide the theory reference for insulation structrue design.In order to research the liquid discharges in the power equipment insulation structures, and deeply understanding dynamic characteristics of the process of liquid prebreakdown in the insulation structures, the influence of different conditions on the development of the streamer in the process of the discharge, this paper establishs the mathematical model of liquid discharge which include the drift dominated charge continuity equations for positive ion, negative ion and electron densityes which are coupled via Poisson’s equation and include the thermal diffusion equation under the field ionization mechanism. Using the finite element method to the mathematics model used in the simplified physical model formed by needle-sphere electrode, it obtains the2D、1D distribution of the electrical field and the1D distributions of the space charges and temperature. Through the contrast analysis, the results show that streamer results from the space charges coupling the space electric field; Space charges migrates under the electric field to form the electric current which lead to liquid temperature rise because of the joule heating and creat the low density area; The different components of the liquid, voltage amplitude and the gap distance effect the propagation of streamer in the process of the discharge directly.Through the theoretical research and numerical simulation for streamer discharge in the transformer oil, not only help to a better understanding of the mechanism of liquid discharge, control and optimize discharge process, but also can have more understanding to discharge process, which can optimize the existing experiments and make experiment results more correspond the actual application requirement, that can design more reasonable experiment device.