The propagation of positive streamers in a weak and uniform background electric field

Abstract

The results of numerical simulations of a positive streamer development in air in a weak and uniform electric field are presented. Streamer dynamics is considered in an electrode gap of 33 mm in length and the configuration was 'protrusion on a plate-plate'. This particular configuration was chosen in order to perform direct comparison between simulated results and experimental data. The electrostatic field in such a system decreases rapidly with increase of the distance from the protrusion (anode) and the region with a weak and uniform background field covers ∼30 mm of the gap. The parameters of the propagating streamer are studied at six different values of the background field strength: 0.24; 0.30; 0.345; 0.37; 0.43 and 0.50 MV m −1 . Stable streamer development (with constant velocity) takes place in a field of 0.5 MV m −1 (the stability field) but the streamer is able to cross the gap in a background field of 0.3 MV m −1 . These values are in excellent agreement with experimental data. During the stable streamer propagation, the electron density and plasma conductivity in the discharge channel and the electric field at its front remain constant. In a background field lower than 0.5 MV m −1 , the discharge front velocity and the electric field at the front decrease linearly with an increase of streamer length. The discharge propagation in the stability field is associated with an increase of electrostatic energy at the streamer front but it decreases if the streamer develops in a weaker electric field. This behaviour is accompanied by a constant Joule dissipation at 0.5 MV m −1 and decreasing energy losses at the streamer front in a weaker background electric field.

Field-Time Breakdown Characteristics of Air, N2, CO2, and SF6

“…For example, ̅ in air at atmospheric pressure increases from 0.13•10 6 m/s at 4•10 6 V/m, up to 5.7•10 6 m/s at 115•10 6 V/m. These values are in the range of those reported in the literature: [18] indicates that the average velocity of streamers in air is (0.1-10)•10 6 m/s; while [50] and [51] provide the value of 2•10 6 m/s for this velocity. As can be seen from Figure 6, ̅ for CO 2 is similar to that for air, for all values of E/N, [52].…”

The inception of pulsed discharges in air: simulations in background fields above and below breakdown

“…The second seed has an isotropic Gaussian distribution for electrons and ions in three spatial dimensions. Such seeds have frequently been used to study the formation of positive streamers in point-to-plane gaps [54,55,56]. The Gaussian distribution we use here has a peak density of 2.3 × 10 13 cm −3 and a width of 0.3 mm.…”

Characteristics of streamer propagation along the insulation surface: influence of dielectric material

“…A spark discharge of air gap or an arc discharge along insulation surface covers a sequence of several processes: the occurrence of initial seeding electrons, the development of electron avalanches, the formation and the subsequent propagation of a streamer, the streamer-to-leader transition and, depending on the energy supply, the formation of a spark or an arc discharge [1]. The streamer is the most critical and complex stage of the electrical breakdown, and is important in the determination of electrical breakdown characteristics of the electrode gap.…”