Particle dynamics and breakdown in SF6 insulated systems under high direct voltage

The paper summarizes a theoretical and experimental investigation, carried out at IREQ, into the behaviour of conducting particles in SF₆ under direct voltage stress. The theoretical investigation covered particle charging, detachment and motion in the SF₆ gap as well as the prediction of breakdown using a modified streamer criterion. Direct voltage breakdown experiments were carried out with coaxial electrodes in compressed SF₆. The parameters investigated involve the polarity of the high voltage electrode, gas pressure and particle size. Whenever possible, the theoretical and experimental results were compared.