Future developments in SF/sub 6/ circuit-breakers and their likely benefits on users

The use of SF/sub 6/ puffer circuit-breakers is now well established throughout the complete range of high voltage and medium voltage applications. These circuit-breakers have established an excellent service record in reliability and efficiency. Manufacturers have investigated the possibility of other SF/sub 6/ interruption techniques which might offer further benefits. In particular, considerable efforts have been made to reduce the required operating energy, further reduce contact erosion and to allow operation at very low SF/sub 6/ filling pressures. The techniques considered are that of rotating arc and autoexpansion. The rotating arc is described only briefly. Autoexpansion (the combination of rotating arc and self expansion) however is relatively new and is therefore discussed in some detail.