Fundamental physicochemical properties of SF6-alternative gases: a review of recent progress

Environmental considerations are increasingly taking a front seat in all arenas of our daily lives. Among the major concerns are greenhouse gases and the resulting global warming problem. Although sulfur hexafluoride (SF6) is the most widely used insulation and arc-interruption medium in electrical power equipment, it is an extremely potent greenhouse gas with a very high global warming potential (GWP). Hence, the global power industry has been actively seeking SF6-alternative gases for decades. In recent years, much progress has been made in developing promising new gases that have dielectric properties similar to, or even better than, SF6 but with much lower GWPs. Many engineering-oriented tests have been performed on the technical performance of these gases and some manufacturers have announced their application in pilot projects. However, their large-scale application still seems premature, in particular because of the lack of some critical fundamental physicochemical information for these relatively novel compounds. To provide a better understanding of these SF6-alternative gases, this paper reviews the recent advances in obtaining their fundamental physicochemical properties, emphasizing basic data calculations and fundamental experiments. The most important properties are analyzed comprehensively. These include the basic physical properties of arc plasmas formed from the gases, decomposition characteristics, materials compatibilities, swarm parameters, cross-sections and some dielectric properties. Finally, perspectives on current research and future research directions are presented.