The behaviour of SF6 puffer circuit-breakers under exceptionally severe conditions

The development of transmission power systems and industrial power systems places high voltage circuit-breakers in operating conditions much more severe than those taken into account by the Standards. Two situations are discussed: - the case of very long lines for which difficulties encountered upon the energisation and de-energisation of no-load lines and upon shunt reactor switching are reviewed; - the case of powerful transformers with low impedance voltage whose high natural frequency is at the origin of a severe transient recovery voltage when a fault takes place on the secondary side of the transformer. In both cases, it is demonstrated that the SF6 puffer circuit-breaker has a satisfactory behaviour though some of the conditions under consideration are exceptionally severe. It is generally unnecessary to resort to the use of auxiliary resistors, except for the energisation of long HV lines. *Report number 13.08 presented at CIGRE, Conférence Internationale des Grands Réseaux Electriques (International Conference on Large High Voltage Electric Systems), session in 1978.