Tuning Nanofillers in Sprayed Coating Toward High Flashover Strength

Abstract

Various surface modification methods have been developed to improve flashover strength in gas–solid composite insulation, among which composite coating is recognized as a flexible and promising approach. However, there is still limited knowledge about the effect of different nanofillers on the surface insulation properties of nanocoating. To this end, spraying coating of high concentration of nanofillers is developed as a universal strategy to improve surface flashover strength and hydrophobicity, in which the nanofillers are tuned to achieve high flashover strength. Five kinds of nanofillers including Al2O3, SiO2, TiO2, SiC, and ZnO are introduced to fabricate the coatings. The effect of nanofillers physical properties on surface trap characteristics and micro-topography is explored to guide the development of coatings and understand the underlying mechanism. Micro-nanoscale hierarchical morphology or porous structure are created in the spraying process, which hinders the development of collision ionization and enhances the flashover voltage of all kinds of coatings. Shallow traps are introduced in the coatings with semi-conductive fillers such as ZnO, SiC, and TiO2, which is beneficial to charge dissipation. Owing to the combined effect of accelerated charge dissipation and hindrance of collision ionization by nanosized pore structures, the SiC coating presents largest enhancement of flashover strength among all coatings, with an increment of 50.3%. The spraying coating of high centration of nanofillers provides a universal strategy for simultaneously improving the flashover strength and hydrophobicity.