Metal Particle Behavior between Dielectric-Coated Electrodes under DC Voltage

Suppressing the activity of metal particles is a key issue in the development of dc gas-insulated power transmission lines (GILs). This study investigates the effects of five different dielectric coatings of the electrodes-namely surface oxidation treatment and four different coating materials (i.e., 1032K high-resistance paint (1032K), teflon, epoxy marlin orange primer (EM primer), and iron red primer (IR primer) spray)-on the movement characteristics of ball and block metal particles under dc voltage and polarity reversal voltage in an SF6 gas environment at an absolute pressure of 0.3 MPa. The results showed that the surface oxidation treatment of the electrodes had little effect on suppressing the particle activity. The coating in the high-voltage electrode did not significantly change the particle jumping voltage, and once the particles jumped, they were adsorbed onto the coating. Coating the ground electrode significantly increased the jumping voltage of the particles. Under dc voltage, the lifting field strength of the particles exceeds 5 kV/mm which is much higher than the maximum design field strength at the ground electrode of dc GIL. The increase in coating thickness did not significantly improve the jumping field strength. Under polarity reversal voltage, the jumping field strength of the particles was lower than under dc. However, the coating of the ground electrode also had a significant effect on suppressing the particles during the reversal process. Simulation results showed that the coating hindered the charge exchange between the particles and the electrode, increased the field strength at the contact position between the particles and the electrode, and reduced the field strength on the side of the particles away from the electrode.