SF₆ is widely used in the industrial field due to its stable structure and excellent properties. It is mainly used in electrical insulation equipment. Due to the boiling point of SF₆, its use in extremely cold regions has been limited. It is harmful to the health of practitioners due to the toxicity of decomposition products. The gas has limited its wider use because of its strong greenhouse effect. As a result, researchers and electrical equipment manufacturing companies around the world are gradually searching for new environmentally friendly gases and have conducted research and exploration on theory and experiment. In this paper, the current status and existing problems of SF₆ are summarized. The research contents and research methods of SF₆ alternative gas direction are reviewed from the aspects of insulation performance, interrupter performance, and decomposition performance. The existing research results of the natural gas, SF₆ mixed gas, perfluorocarbons, and C_nF_mX gas are summarized, and the future development trend of alternative gas for SF₆ in the electrical industry is proposed.

To verify the feasibility of replacing SF6 by CF3I/N2, we compared their power frequency breakdown performance with the influence of gas pressure, mixing ratio, and electric field utilization coefficient. Under different electric fields and mixing ratios, the power frequency breakdown voltage of CF3I/N2 increases linearly along with gas pressure. Besides, with the rise of the electric field utilization coefficient, the linear growth rate of breakdown voltage along with gas pressure gradually rises. The sensitivity of pure CF3I to electric field is particularly high and can be improved by the addition of N2. The mixture 30% CF3I/70% N2 at 0.3 MPa could replace pure SF6 in equipment requiring a low insulation, but the gas pressure or the content of CF3I need to be increased for higher insulation requirements.

This paper is devoted to the calculation of fundamental properties of CO ₂ mixed with C ₂ F ₄ . The species composition and thermodynamic properties (mass density, entropy, enthalpy and specific heat at constant pressure) are based on Gibbs free energy minimization. The transport properties (electrical conductivity, viscosity and thermal conductivity) are calculated by the well-known Chapman-Enskog method. The Lennard-Jones like phenomenological potential and some recently updated transport cross sections are adopted to obtain collision integrals. The calculation is developed in the temperature range between 300 and 30 000 K, for a pressure between 1 to 16 bar and for several C ₂ F ₄ proportions. Transport coefficients for CO ₂ are also compared with previous published values, and the reasons for discrepancies are analyzed. The results obtained for CO ₂ –C ₂ F ₄ mixtures provide reliable reference data for the simulation of switching arcs in CO ₂ circuit breakers with the ablation of PTFE.

This paper has for objectives to present the radiative and the transport properties for people beginning in thermal plasmas. The first section will briefly recall the equations defined in numerical models applied to thermal plasmas; the second section will particularly deal with the estimation of radiative losses; the third part will quickly present the thermodynamics properties; and the last part will concern the transport coefficients (thermal conductivity, viscosity and electrical conductivity of the gas or mixtures of gases). We shall conclude the paper with a discussion about the validity of these results the lack of data for some specific applications, and some perspectives concerning these properties for non-equilibrium thermal plasmas.

C₄F₈-CO₂ mixtures are one of the potential substitutes to SF₆ in high-voltage circuit breakers. However, the arc quenching ability of C₄F₈-CO₂ mixtures is still unknown. In order to provide the necessary basic data for the further investigation of arc quenching performance, the compositions, thermodynamic properties, transport coefficients, and net emission coefficients (NEC) of various C₄F₈-CO₂ mixtures are calculated at temperatures of 300–30 000 K in this work. The thermodynamic properties are presented as the product of mass density and specific heat, i.e., ρC_p. The transport coefficients include electrical conductivity, viscosity, and thermal conductivity. The atomic and molecular radiation are both taken into account in the calculation of NEC. The comparison of the properties between SF₆ and C₄F₈-CO₂ mixtures is also discussed to find their differences. The results of compositions show that C₄F₈-CO₂ mixtures have a distinctive advantage over other alternative gases e.g., CF₃I and C₃F₈, because the dissociative product (i.e., C₄F₆) of C₄F₈ at low temperatures has a very high dielectric strength. This is good for an arc quenching medium to endure the arc recovery phase. Compared with SF₆, C₄F₈-CO₂ mixtures present lower ρC_p at temperatures below 2800 K and larger thermal conductivity above 2800 K. Based on the position of peaks in thermal conductivity, we predict that the cooling of C₄F₈-CO₂ arc will be slowed down at higher temperatures than that of SF₆ arc. It is also found that the mixing of CO₂ shows slight effects on the electrical conductivity and NEC of C₄F₈-CO₂ mixtures.

This paper focuses on the modeling of a hydrogen arc column at very high pressure (20 bar). The problem is solved from Elenbaas-Heller equation where the radiation is carefully considered with the net emission coefficient. The absorption spectrum requires the integration of background continuum, molecular bands, and line spectra. This work directly aims to predict the electric current-voltage characteristics which is key for the design of new processes. We propose also a new analytic solution which generalizes the channel model of electric arc to the case when the volume radiation makes a significant contribution to the energy balance. The presented formalism allows a better determination of the plasma thickness parameter R_p for net emission coefficient method in cylindrical arcs and gives satisfactory results in comparison to earlier experimental works on high pressure hydrogen plasma.