Surface charge measurements on epoxy spacer in HVDC GIS/GIL in SF6

The design of reliable high voltage equipment remains a challenge nowadays. The surface charge accumulation at gas/solid interface is a major problem for HVDC GIS/GIL. The electric field can be distorted and the dielectric strength of the system can be thus reduced dramatically due to surface charges. This paper presents the measurement of surface charge (surface potential) on spacer in DC GIS/GIL under pressurized SF₆ condition. The surface potential distribution on the spacer is obtained by an electrostatic probe connected to a displacement system. Firstly, the importance of preparation process for DC GIS/GIL spacer for the measurement of surface charge is introduced. The influence of DC voltage, electrode roughness on the surface charge accumulation and the time constant of the system is then investigated. The dominant mechanism for surface charge accumulation is also identified.