Abstract
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.
Highlights
GAS insulated transmission line (GIL) has a broad development prospect due to its characteristics such as high voltage level, large transmission capacity, little electromagnetic radiation, and substantial laying flexibility [1,2]
Lifting voltage of spherical, linear and sheet metal particles, the suppression effect of movement activity, as well as the gas-gap discharge caused by particles
2) Compared with the common coating methods with the binder, the PI/TiO2 nanocomposite film with TiO2 nanoparticle content of 16wt.% and the thickness of 25 μm without adhesive coating on the electrode surface proposed in this paper has a better effect on the lifting voltage of metal particles
Summary
GAS insulated transmission line (GIL) has a broad development prospect due to its characteristics such as high voltage level, large transmission capacity, little electromagnetic radiation, and substantial laying flexibility [1,2]. The PET film with a long-term operating temperature of less than 120°C cannot meet the heat resistance requirements of the DC GIL electrode coating, and a film material with good thermal stability should be selected. When the content of TiO2 nanoparticles is too high, the agglomeration phenomenon will destroy the film's stable structure, and the corona resistance time of the nanocomposite film will decrease. The above corona resistance time test shows that, when the content of TiO2 nanoparticles in the PI/TiO2 nanocomposite film is 16 wt.%, the film's corona resistance is more prominent, which can effectively avoid the corona damage and improve the service life of the coating. In this work, PI/TiO2 nanocomposite films with TiO2 nanoparticle content of 16wt.% and thicknesses of 25 and 50 μm were selected as the electrode coating materials
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