Research on Surface Charge Accumulation Characteristics of DC Basin Insulator

When the DC voltage applied, the electric field distribution of the DC GIL basin insulator will change from the initial capacitive distribution to the steady-state resistive distribution. This process is accompanied by the accumulation and dissipation of surface charges, which may cause a decrease in the flashover voltage along the insulator. Therefore, it is of great significance to study the charge accumulation characteristics of basin insulators under DC voltage. In this paper, a DC GIL experimental platform is built, and a set of surface charge measurement system based on electrostatic probe method is established. The surface charge accumulation characteristics of basin insulators and the transformation of main accumulation methods are studied in 0.4MPa SF6 gas. The results show that: the surface charge distribution of basin insulators is related to the DC voltage amplitude and applied time. At low voltage amplitudes, the concave side of the insulator mainly accumulates negative charges (opposite to the applied voltage), and the charge source is mainly conducted on the solid insulation side; At high voltage amplitudes, the concave side of the insulator mainly accumulates positive charge (the same polarity with the applied voltage), and a small amount of negative charge accumulates near the ground electrode. Positive and negative charges coexist on the surface of the insulator, and the charge accumulation gradually transforms into gas side conduction. As the applied voltage time increases, the surface charge of the insulator reaches saturation, and the saturation time is about 60 minutes.