SF6 gas breakdown at low temperature

The low-temperature breakdown behavior of compressed SF₆ is reviewed, the scope of the investigation being limited by experimental conditions which correspond to a gas state of the insulating medium. A thermodynamic model has been developed taking into account the nonideal gas behavior associated with compressed gas conditions and a low-temperature environment. The accuracy of the thermodynamic model was checked successfully by comparing predicted and measured dew points for SF₆ and mixtures with N₂. A brief analytical review of a rather sparse set of low-temperature breakdown data in SF₆ shows that the low-temperature environment has a definite effect on gas-breakdown behavior; in some circumstances, the effect is large enough to require practical modifications. Some of the data obtained are analyzed in the framework of compressed-gas discharge phenomenology in order to link this temperature dependence of breakdown with some underlying active mechanisms