Effect of SiO₂ nano film deposited on copper and aluminium electrodes on the power frequency breakdown voltage of SF₆ gas

In order to reveal the effect of insulating nano film on the insulation strength of SF6 gas gap, SiO2 nano film was deposited on the electrode surface by the plasma-enhanced chemical vapour deposition technique. The power frequency breakdown characteristics of SF6 gas under Cu and Al electrodes were obtained before and after coating. The results showed that when the Cu electrode was coated, the breakdown voltage was up to at most 11.5% higher than that of an uncoated Cu electrode in the pressure range of 0.2-0.5 MPa. When the Al electrode was coated, the breakdown voltage of SF6 gas was lower than that of an uncoated one in the pressure range of 0.2-0.5 MPa. The breakdown voltage of SF6 gas under the Cu electrode was slightly lower than that under the Al electrode, but the breakdown voltages under the coated Cu electrode were significantly higher than that under the coated Al electrode. Through SEM tests, it was found that the surface roughness of the electrode decreases after coating, but particles were formed on the surface of the Al electrode. The content of metal fluoride formed on the coated Al electrode under multiple breakdowns was significantly higher than that on the coated Cu electrode. The research results could provide references for improving insulation performance of GIS equipment.