Development of a surface charge measurement system for GIS insulator in SF6

Gas Insulated Switchgear (GIS) has been widely applied in the newly-built transformer substation attributed to its advantages of less land occupied and good insulation performance. Under actual operation conditions, GIS will withstand different kinds of voltages, such as DC, AC and impulse voltages. Under these conditions, there will be charges accumulated on the surface of GIS insulators, which can enhance the local electric field and even affect the flashover. In order to study the surface charge accumulation characteristics of actual GIS disc insulator in SF6 under different voltages, a disc insulator surface charge measurement system based on electrostatic capacitive probe is established in this paper. The surface charge measurement devices are controlled by the designed three-dimensional control mechanism, which can drive the probe to scan the insulator surface in both the circumferential and radial direction with high precision (1mm of radial direction and 1° of circumferential direction). The calibration experimental results shows the high precision and high sensitivity of this system. The charge resolution of the probe for the bevel surface could be up to 0.02106pC/(m²·nV) and the space resolution could be up to 6.3 mm², the charge resolution of the probe for cambered surface could be up to 0.0303pC/(m²·nV) and the space resolution could be up to 4.4 mm². The preliminary experimental results of surface charges accumulation on GIS insulator under AC voltage in SF6 which are obtained by designed system ensure the feasibility.