Investigation of particles on insulator surfaces in gas insulated systems under DC stress

With the increasing need of transmitting electrical energy over very long distances, combined with necessary space saving installations, the focus is more and more shifted to DC operated gas insulated systems. Their insulation system is nearly uniform, hence well-known problems, like space charge accumulation and metallic particles become more critical using SF₆ in comparison to non-uniform air insulations. As soon as the applied voltage exceeds the inception voltage at the particle tips, the particle will produce charge carriers. These space charges will accumulate on the insulator and possibly influence the flashover behaviour. For a systematic study, variable parameters as the size of the particle and its position relative to the high voltage electrode, were chosen. In this paper, the flashover behaviour of epoxy resin insulators with adhesive metallic particles under both positive and negative DC voltage stress in gas insulated systems was investigated.