Numerical Simulation Of Nanosecond-Pulsed Discharge Phenomenon In Transformer Oil And Measurement Of Discharge Spectrum

Research of liquid dielectrics discharge characteristic has been focused on the field of electrical insulation,the main purpose is to take full advantage of the insulating properties of the liquid medium,and further improve and optimize the insulation design.With the rapid development of pulsed power technology,research of liquid dielectric discharge process under nanosecond-pulsed voltage has been widely concern.Therefore,this dissertation establishes a two-dimensional hydrodynamic model,and makes a numerical simulation on discharge process of transformer oil on electric field strength,space charge density,temperature variation and the formation and propagation process of streamer,The streamer discharge profile and distributions of electric field and space charge density are obtained under different conditions such as the amplitude of applied voltage,rise time and electrode structure.Results show that space charges enhance the front field of streamer head under 0.1/2μs nanosecond-pulse voltage,which is conducive to the longer propagation of discharge channel.While the magnitude of applied voltage are 200、230 and 260kV,it can be observed that the higher the applied impulse voltage,the faster the streamer propagates;needle-plate electrode is better the streamer development than the needle-sphere;the voltage amplitude fix for 300kV,the streamer radius of 10ns rise time is maximum,and the electric field is minimum under nanosecond-pulse voltage of rise time 10,50 and 100ns.Furthermore,utilizing the optical effect of the liquid dielectric in the discharge process,the dissertation design the discharge spectrum acquisition systems of 45#transformer oil,the spectral measurement apparatus comprise spectrometer,ICCD,fiber optics and computer.The spectrum information during the discharge of transformer oil is collected by them,and then converting the analog signal into a digital signal by the computer,the form of the spectrum chart is presented in WinSpec software,the experimental data obtained by the spectral characteristics of some carbon spectrum line,but the most frequent is the Ha spectral line,and strength is large,indicating that the more particles involved in such particles transition;in one discharge,the intensity of hydrogen spectral lines will become increasingly large,which express as the number of particles generated by the discharge are more and more;also the electron excitation temperature and electron density of the discharge area is given according to the spectrum information.Liquid discharge spectroscopy provides an experimental method for analyzing discharge from the microscopic view,the study for the discharge mechanism of liquid dielectric has important reference value.