Electron energy distribution and transport coefficients of electron swarms in SF₆and nitrogen mixtures

Abstract

Electron swarm behaviour in SF6 and nitrogen mixtures is analysed over the E/N range from 141 to 707 Td by a three-term Boltzmann equation method. A set of electron collision cross sections, which was determined consistently with measurements for the respective pure gases by the authors ((SF,, ltoh et a/ (1988); N2, Ohmori et a/ (1988)), is used. The calculation is carried out for the steady-state Townsend (SST), pulsed Townsend (PT) and time-of-flight (TOF) experiments. In particular the TOF parameters of these mixtures are deduced for the first time as far as the authors are aware. It is found that the calculated values of the effective ionisation coefficient E shows a monotonic variation with percentage of SF, at a fixed E/N, the same as previous measurements. The E/N value at which E = 0, i.e. the limiting E/N, is also deduced and in close agreement with measurements. The variations of the electron energy distribution and other transport coefficients with the partial SF6 pressure are calculated and discussed in detail.

Simulation of limiting field behavior in electron swarms in SF/sub 6/+N/sub 2/ gas mixtures

“…At lower E / N , as the SF6 content of the mixture increases, the mean energies increase while at high E / N values the tendency reverses. Similar behavior of the mean energies in SFs+Nz mixtures has been observed recently in a three-term Boltsmann equation method[7].4. CONCLUSIONSH E limiting E / N values in SFs+Nz mixtures are eval-T uated directly by a Monte Carlo simulation technique rather than deducing these values from the plots of effective ionieation coefficients as a function of E / N .…”

“…Therefore, (E/N)l;,,, is an important parameter to predict the electrical insulation characteristics in electronegative gas or gas mixtures. However, this parameter is usually deduced from the graphs of the variation of the effective ionization coefficient d with respect to E / N at a given mixture ratio [7,8], although ? ?Boltzmann-type calculations can be used to obtain the limiting field value numerically.…”

Prediction of the critical reduced electric field strength for carbon dioxide and its mixtures with copper vapor from Boltzmann analysis for a gas temperature range of 300 K to 4000 K at 0.4 MPa

“…Most previous studies of gas dielectric breakdown properties have concentrated on room temperature values. [13][14][15][16] For these reasons, it is important to study and better understand the dielectric properties of hot gas mixtures.…”

Kinetic behaviors and dielectric strength of SF<inf>6</inf> and N<inf>2</inf> over the E/N range from 160 to 650Td

“…SF is an electronegative gas, and possesses very high dielectric strength, but its GWP is much higher than that of 2 CO , so it has been listed as one of the restricted gases in Kyoto protocol signed in 1997. Some researches indicated that when 2 N , 2 CO and air are added into 6 SF , the mixtures electric strength are comparable to that of 6 SF , their GWP are much little, and the feasibility had been proved by many experiments.…”

“…Some researches indicated that when 2 N , 2 CO and air are added into 6 SF , the mixtures electric strength are comparable to that of 6 SF , their GWP are much little, and the feasibility had been proved by many experiments. Among of them, 6 2 / SF N mixtures had been used in industry preliminary [1].…”