Transient Ground Potential Rise in Gas Insulated Substations - Experimental Studies

The very rapid dielectric breakdown of SF6 (eg, during the operation of disconnect switches in gas-insulated substations) generates steep-fronted travelling waves which couple to the exterior enclosure surface at the air/SF6 bushings and cause transient ground potential rise. These high voltage transients, which can be in the 100 kV range, propagate from the air/SF6 termination, along a transmission line defined by the bus enclosure and the ground plane, toward the switchgear. This paper presents a theoretical and experimental investigation of the phenomenon, from which the basic mechanisms have been identified.