Vacuum disconnectors: Acceptability issues

SF6gas is widely used in MVdistribution switchgear because of its outstanding performances in fulfilling the three functions : switching insulation and disconnection. However it has been identified as a green-house gas whose release in atmosphere should be avoided : therefore other technologies are considered to substitute SF6, such as vacuum switching and solid insulation. Recently vacuum interrupters (Vis) have been proposed also to perform the disconnecting function : the purpose of this paper is to evaluate the suitability of vacuum technology for this application. The first part about disconnectors in general is a reminder of their definition, purpose and technical requirements. The second is centred on the properties of vacuum insulation and its suitability to provide a reliable isolating distance between open contacts. The third is a review of various solutions proposed to overcome the difficulties raised by the use of vacuum as an insulating medium for disconnecting function. Finally the acceptability of these solutions is discussed.