Partial discharges inception and ageing effects in a gas insulated HV equipment

Charge transfer occurring between materials of different nature when they are put into contact is a well known phenomenon. In the first part of the paper it is shown how the transposition of this phenomenon to the metal/insulator interfaces in gas insulated HV equipments can explain why such interfaces constitute weak points in HV insulation technologies. Following from the first part of the paper, the second part is more especially devoted to the processes initiating the surface ageing of the insulators: the gas activation processes induced by the partial discharges and the resulting chemical processes leading to the formation of conducting electrolytic layers on their surface.