Effects of H2O and O2 Impurities on the Trichel Pulses Characteristics of the Negative Point-Plane Corona Discharge in SF6

The results of numerical simulation of the effects of H2O and O-2 impurities on the Trichel pulses characteristics in the negative point-plane corona discharge in SF6 gas at 0.4 MPa is presented in this paper. The H2O and O-2 contents varied from 200 ppm to 10,000 ppm. The continuity equations for three charged species along with Poisson's equation were solved simultaneously to obtain the Trichel pulses characteristics in SF6/H2O mixtures and SF6/O-2 mixtures. The reduced ionization coefficient, the reduced attachment coefficient, the electron mobility and the electron diffusion coefficient for SF6/H2O and SF6/O-2 mixtures were determined by solving the two-term Boltzmann equation. The effects of H2O and O-2 on the current pulses, the distributions of the charged species and the reduced electric field at the instants of the first and second peak pulse, the time-dependent total number of the three charged species in the gap and the reduced electric field at the discharge tip were investigated to determine the sensitivities of the Trichel pulses characteristics of the SF6 to the H2O and O-2 impurities.