Measurement and modeling of surface charge accumulation on insulators in HVDC gas insulated line (GIL)

Gas insulated lines are a means of buck electric power transmission at high or extra high voltage. They have been used for linking GIS to overhead lines or to power transformers in AC power systems for over four decades. However, nowadays, the design of a HVDC GIL with the same reliability as HVAC remains a challenge. It is mainly due to the charge accumulation on the insulator surface under DC field, as a result of a substantial distortion of the initial field and an unexpected decrease of flashover voltage. The paper introduces a surface charge measurement system based on a 220 kV GIL unit. The surface potential distribution on the insulator is obtained. A model is also provided to help to understand the surface charge accumulation process. The results in this paper may be useful for the…