Recent trends in development of high voltage circuit breakers with SF₆ alternative gases

The available knowledge of state-of-the-art of SF₆ alternative gases in switching applications was collected and evaluated in an initiative of the Current Zero Club [1] together with CIGRE. The present contribution summarizes the main results of this activity and will also include the latest trends. The main properties and switching performance of new gases are compared to SF₆. The most promising new gases are at the moment perfluoroketones and perfluoronitriles. Due to the high boiling point of these gases, in HV applications mixtures with CO₂ are used. For MV insulation perfluoroketones are mixed with air, but also other combinations might be possible. The dielectric and switching performance of the mixtures, with mixing ratios that allow su ciently low operating temperatures, is reported to be only slightly below SF₆. Minor design changes or de-rating of switchgear are therefore necessary. Di erences between the gas mixtures are mainly in the boiling point and the GWP.