The gas SF6 provides a combination of favourable properties such as high dielectric strength, excellent arc quenching ability, chemical inertness, high thermal stability, non-flammability and very low toxicity. It is colourless and odourless. The excellent quenching and insulating properties of SF6 have permitted the construction of completely new types of high-voltage circuit breakers and switching stations with outstanding features:
- compact and space-saving design
- low noise levels
- protection against accidental contact of live parts
- protection against intrusion of impurities
- elimination of fire hazard
Substations using SF6 are particularly in demand where, on account of limited space, a compact design is required. These substations occupy only 10-15 % of the space required by conventional units. New SF6 filled equipment can thus be installed in densely-populated areas where site costs would prohibit the use of traditional methods. Thanks to their insensitivity to polluted air, enclosed outdoor versions of SF6-insulated substations are installed in the chemical industry, in desert regions and in coastal areas.