Numerical Simulation And Experiment Of Electron Avalanche Process For Air Insulation In Short Gap

Electric power is a kind of energy which can be easily centralized and transmitted and distributed and controlled and conversed into other kinds of energy, and it is also the substantial foundation of modern civilization society. High voltage transmitting lines of electric power system depend on enough air gaps to keep insulating clearance. Furthermore, most of switch equipment of substation is gaseous insulated. Gas discharge is a subject of researching electron motion law and its application under the electrical fields. Experimental research and theoretical analysis of the gas discharge mechanism have academic signification and practical value in understanding the law of gas discharge under different electrodes and different conditions for developing new type high voltage apparatus in order to ensure the electrical apparatus operating safely and reliably. Scientists have made lots of researching work in questing phenomena of gas discharge and gained great achievement,but there is no an ideal model to describe the gas discharge process because it concerns lots of affecting factors and different aspects of substance microstructure (including electron, atom, molecule and photon). According to the electron collision ionization theory of Townsend, the electron avalanche is the basic process in gas discharge. In the thesis, after investigating the literatures of gas discharge field at domestic and abroad, based on the Townsend and streamer theory, according to the Raether and Meek criterion, the mathematics model of the electron avalanche in gas insulated short gap is constructed and the processes of the electron avalanche growth are simulated by computer. Under the plane-plane and point-plane and point-point and sphere-sphere and sphere-plane and sphere-point electrode systems, the electron avalanche growth process is simulated by computer under fully considering the space charge fields of the electrons and the positive ions, meanwhile, the behaviors of charged particles in electrical field have been taken into account in the calculation procedures, which include ionization, attachment, drift, diffusion and density of gas molecule. Simulation results show that the space charge field in the negative point electrode system affects the electron avalanche development more greatly than that in positive point electrode system does; the effect degrees are relative to density of gas molecule. The simulation experiments of various kinds of electrode system under different pressure show that the gas inceptive when the gap is fixed, discharge voltage is proportional to the pressure; because the degree of uniformity of electrical field is different among the electrode systems, the changing trend of the inceptive discharge voltage with the pressure is unlikeness. The conclusions of this thesis could offer technology support and reference to design insulation coordination of gas insulated high voltage equipment and outdoor insulation structure of transmitting lines.