Evaluation of Sustainable SF6 Alternative Gas Mixtures Used in Electric Power Equipment

Abstract

Sulfur hexafluoride, SF6, has been the preferred dielectric medium in electrical power applications for decades. However, due to its extremely long atmospheric lifetime and very high global warming potential the industry is designing SF6-free technologies for many applications, including switchgear, circuit breakers and gas-insulated lines or bus bars. Alternative gas mixtures incorporating a fluoronitrile or a fluoroketone have low climate impact and are being successfully used in gas-insulated equipment currently operating on the grid in Europe. This paper reviews the toxicological studies conducted on these gases and the parameters required to perform a risk assessment for their use in electric power applications. The toxicological studies demonstrate that the alternative gases are low in acute inhalation toxicity which is the primary mode of potential exposure to an insulating gas. The occupational exposure limits established for these SF6-alternatives are well above the typical concentrations of insulating gas found near electric power equipment. In the event of accidental release of insulating gas, the alternative gas mixtures present potential exposure risks similar to those exhibited with SF6-filled equipment. Thus, these alternative gases and their mixtures provide a wide margin of safety required for these applications.