Effect of Electrostatic Probe Online Measurement on Surface Charge Distribution for HVDC GIL

In this article, a 3-D simulation model of surface charge accumulation for 200-kV dc gas-insulated transmission line (GIL) basin insulator is constructed. Meanwhile, the whole process of electrostatic probe online measurement is established, and the motion process of electrostatic probe is simulated by the dynamic grid module in finite element software. The key factors in electrostatic probe online measurement are considered comprehensively, including the probe initial position, central conductor potential, probe measuring time, and measuring position. The variation of surface charge density and surface normal electric field after online measurement is calculated and analyzed. The results show that the surface charge density near the probe center is obviously affected after online measurement, while the surface charge density in the region far away from the probe is less affected. When the distance ${D}$ between the probe initial position and the insulator surface is less than 10 mm, the polarity of the surface charge at the measured point will be reversed. When ${D}$ reaches 100 mm, the change rate of the surface charge density is less than 5%. In addition, with the increase of the central conductor potential and probe measuring time, the surface charge density at the measured point decreases more after online measurement. When the probe measures at the same position for more than 3 min, the surface charge density decreased by more than 30%. Moreover, the closer the probe is to the central conductor, the more the surface charge density is reduced after online measurement. This study can provide reference for the online measurement technology of dc GIL insulator's surface charge density.