Suppression on Particle Movement and Discharge by Nanocomposite Film Coating on DC GIL Electrode Surface

The metal particles’ movement in DC GIL can easily result in gas-gap breakdown or insulator surface flashover, which will seriously reduce GIL’s insulation performance. To suppress the particle movement and discharge, the authors manufactured the colloidal PI/TiO2 nanocomposite film by the in-situ polymerization method and coated the film on the electrode surface. This paper characterized and tested the film’s physicochemical properties and analyzed its influence on the lifting voltage and movement activity of spherical, linear, sheet metal particles. The results show that TiO2 nanoparticles disperse evenly in the polyimide matrix with excellent compatibility between inorganic and organic phases. As nanoparticles’ content increases, the composite film’s mechanical performance and electrical strength decrease, and the corona resistance time increases first and then decreases. Nanocomposite films can significantly increase the lifting voltage of metal particles. The lifting voltage is almost the same, whether it is the bottom-electrode coating or dual-electrode coating. Voltage polarity does not affect the lifting voltage; however, as the film thickness increases, the lifting voltage increases. After coating, the metal particles’ movement decreases and gradually the particles lie on the bottom electrode’s surface. In the meanwhile, the gas-gap discharge process also stops. There is an obvious polarity effect for the movement of metal particles. The bottom-electrode coating method should be adopted for DC positive voltage, while the dual-electrode coating method should be adopted for DC negative voltage.