Study On Discharge Behaviors Of Short SF₆ Gap With Dielectric-covered Electrodes

Discharge with dielectric-covered electrodes is a special discharge model with the electrode is covered by the insulated dielectric. It is also one of the main devices to generate low temperature plasma in the industry, so a lot of research about its discharge characteristics in common gas have been carried out extensively. But there are few reports on the discharge phenomena of SF₆ with dielectric-covered electrodes, especially about its discharge characteristics under different excitations and structures. Because of the high dielectric strengths of SF₆, it has been a main insulating dielectric. There are insulation structures which are similar to dielectric-covered electrodes in the electrical equipments which use SF₆ as insulation, so systematically analyzes the inluence facots about applied voltage and structure parameters would have practical implications.An equivalent circuit and fluid model are respectively discussed and 1-D self-consistent hydrodynamics of gas discharge model is established in the dissertation, including particle kinetics equation and Poisson equation and an SG algorithm to combineit with a discretization.Time evolution and behavior of microscopic particles, such as current density, field intensity and particle density are taken as the characteristic parameter which characterizes the dynamical behavior of the short SF₆ gap discharge with dielectric-covered electrode under sine and nanosecond pulse have been calculatedwhich proves the negative electric field caused by the accumulation of charged particles on the dielectric is the main reason of why SF₆ with dielectric-covered electrodes is hard to develop into a continuous discharging.Compared with the discharge initiated by millisecond sine voltage discharge current under nanosecond shows obvious bipolar.Parameters effect like applied voltage and structures have been discussed. The results show that the current density and charged particle density will increase as the growth of voltage amplitude. However the effects on them are different as the change of gap width and covering methods which need to be illustrated separately. Overall, compared with the conventional form of discharge, discharge with dielectric-covered electrodes presents its distinctiveness. All the characteristics above can be explained by means of analyzing particle behaviors. Experiment of discharge with dielectric-covered electrodehave been designed and the pulse currentsignals can be measured through the improved Rogowski coil sensor. The experimental results indicate that the discharge current waveform excited by the nanosecondunipolarity pulse shows an obviousbipolar pattern which is same as the simulation results.