Dynamic Characteristics of SF₆-N₂-CO₂Gas Mixtures in DC Discharge Process

Abstract

Dynamic characteristics of discharge particles are described within the framework of a two-dimensional photoionization-hydrodynamic numerical model for the discharge process of SF6-N2-CO2 gas mixtures at atmospheric pressure, under a uniform DC applied field. The finite difference-flux corrected transport (FD-FCT) algorithm is used in the numerical implementation for improving the accuracy and efficiency. Then the tempo-spatial distributions of the gap-space electric field and electron velocity are calculated from the microscopic mechanism, and the dynamic behaviors of charged particles are obtained in detail. Meanwhile, the tempo-spatial critical point of the avalanche-to-streamer in this model is discovered, and several microscopic parameters are also investigated. The results showed that the entire gap discharge process can be divided into two phases of avalanche and streamer according to Raether-Meek criterion; the electron density within the discharge channel is lower compared to that of positive and negative ions; space charge effect is a dominant factor for the distortion of spatial electric field, making the discharge channel expand toward both electrodes faster; photoionization provides seed electrons for a secondary electron avalanche, promoting the formation and development speed of the streamer.

A new approach for dielectric breakdown calculation of residual hot gas after arc burning based on particle transport and Boltzmann analysis

“…Wu et al applied this method to the discharge in N 2 and SF 6 -N 2 . Morrow et al carried the photon ionization calculation for 2D streamer simulation [33,37], which was widely used in the simulation of SF 6 discharge [38][39][40] and adopted in this work.…”

“…When t = 0, the number densities of the electron and ion are both equal to 10 −5 m −3 while the number density of neutral particles is zero. As in [39], a seed charge was put near the cathode as the initial condition, which follows the Gaussian distribution along the axial direction, with a peak number density of n G = 10 6 m −3 and a Gaussian radius of r G = 2.5 × 10 −4 m. In this section, the discharge in SF 6 between the electrodes with 2 mm distance, at room temperature and atmospheric pressure has been calculated, as shown in figure 10. The development of the avalanche is mutually affected by electron drift, diffusion, ionization and attachment.…”