Swarm parameters and dielectric strength of a promising eco-friendly SF₆ substitute: Bis(trifluoromethyl) sulfide (CF_₃SCF_₃) and its mixtures

This paper investigates the insulation properties of bis(trifluoromethyl) sulfide (CF₃SCF₃), a gas proposed as an alternative to SF₆. This gas demonstrates excellent comprehensive properties, with a boiling point of approximately −22 °C and a global warming potential of about 2.8. Using a high-throughput pulsed Townsend experiment, the insulation properties of CF₃SCF₃ were investigated. The results indicate that the dielectric strength of CF₃SCF₃ relative to SF₆ is approximately 1.72. Mixtures of CF₃SCF₃ with N₂ and CO₂ exhibit positive synergistic effects. And the ion reaction rate coefficients and electron attachment cross-section of CF₃SCF₃ gas were calculated. Additionally, AC breakdown experiments were conducted to study the influence of operating conditions (e.g. gas pressure and electrode structure) on the insulation strength of CF₃SCF₃ and its mixtures with CO₂/N₂. Combined with saturated vapor pressure analysis, this work explores the feasibility of engineering applications for CF₃SCF₃ gas mixtures. It is shown that, 30% CF₃SCF₃ gas mixture, while meeting the minimum operating temperature requirement of −15 °C, can be pressurized in the range of 0.4–0.6 MPa while providing insulation strength comparable to that of SF₆ at the same pressure. This makes it suitable for use in high-voltage gas-insulated switchgears and transmission lines (GIS and GIL). From the perspective of insulation performance, CF₃SCF₃ gas has significant potential to replace SF₆ in engineering applications.