Surface Charge Measurements in Non-Uniform Air Pressurized Gaps with a Dielectric Barrier

Medium and high-voltage gas-insulated switchgear (GIS) are critical components of electrical power transmission and distribution networks. Due to the F-gas regulation entry into force in 2024, SF6 alternatives need to be found; however, the implementation of natural-origin gases insulation causes an increase in the size of GIS. It has been seen from previous studies that the use of dielectric barriers can enhance the dielectric strength and thus keep compact design. This enhancement is linked to increase of discharge paths but also by surface charge accumulation at gas–solid interfaces. This paper presents an investigation of the surface potential on the dielectric barrier in a DC GIS system under pressurized dry air conditions. The surface potential distribution on the dielectric barrier is obtained using an electrostatic probe connected to a displacement system. The influence of the DC voltage and pressure on surface potential accumulation is then investigated. The surface charge is then deduced from the surface potential. The surface potential increases with the decrease of the pressure. Dust figures are used to visualise the charge distributions and shows a pressure dependence for a fixed surface charge density. Surface charge accumulation for certain configurations can lead to an increase in the discharge path, which no longer follows the shortest path.