The dirt will adhere to the external insulation surface of ordinary electrical equipment after a period of time. Under wet conditions, such as fog, dew, rain and snow, the soluble substances gradually dissolve and form a continuous conductive film, which will reduce the level of electrical insulation on the surface, leading to current leakage, local arc generation, or even breakdown of insulation. This series of phenomena is called pollution flashover. The direct consequence of pollution flashover is that various equipment and devices will be damaged, which endangers production, construction and business activities, and brings inconvenience to people's lives.
There are basically four kinds of measures to prevent pollution flashover from the source:
(1) Cleaning. Cleaning once a year or once a quarter when pollution is heavy , though it is manpower-consuming .
(2) Adjusting and climbing, or using composite insulators, etc. The effect is good, though the price is high.
(3) Coating silicone oil, etc. The validity only lasts for a few months and the cleaning is very inconvenient.
(4) Using anti-pollution flashover coatings. From the perspective of cost-effectiveness and follow-up maintenance, anti-pollution flashover coating
At present, the RTV silicone rubber coating
is widely used, whose single index is acceptable in the respect of anti-pollution flashover, but its comprehensive performance is not high. Silicon atoms centered its umbrella-shaped spatial configuration, and the methyl structure is tightly outside to form a closed surface. When water touches, it forms beads and beads will roll down, so a continuous film will not be formed in a short time. This is called hydrophobic. However, the structure of silicone rubber also makes it difficult to meet the requirements of its mechanical and other properties without reinforcement.
The structure of nano-fluorocarbon anti-pollution flashover coating is quite different from RTV. C-F bond length in organic fluorine resin is very short, basically fluorine atoms outside, forming a cylinder to shield the main chain of carbon, making chemicals, ultraviolet rays and other difficult to penetrate. C-F bond energy is the highest in the single bond, which requires a lot of energy to destroy. More importantly, the copolymer structure is arranged alternately, and the more regular the arrangement is, the more stable the molecule is. What’s more, the intermolecular force is very low, and the surface energy of the whole system is also very low. It is difficult for the coating to be wetted by water and organic matter. This forms hydrophobia and preliminary self-cleaning. Because of hydrophobia, it will not be wetted by water, and dirt will not be ionized, thus current leakage is prevented. The better hydrophobicity, the more outstanding anti-pollution flashover effect. In addition, fluorocarbon resin has chemical inertia and thermal stability because of its low polarizability.
Resin structure determines the basic properties of coatings, and the preparation of coatings with excellent comprehensive properties requires the optimum matching of other components of coatings and their joint contribution. Nanomaterials refer to materials with sizes ranging from 1 to 100 nm. Because of their special properties, ordinary materials exhibit special and even reversal physical and chemical properties. In this study, the contribution of nano-materials to mechanical properties, hydrophobicity, self-cleaning and the availability of raw materials were comprehensively considered, and nano-SiO 2 was selected. At the same time, due to the low temperature environment, external insulation surface icing will also appear flashover, resulting in power outage. Therefore, organic metal compounds are chosen to be added to paint formulations in an attempt to improve this phenomenon. Organometallic compounds are dispersed in coatings in a sol state. The metal oxides formed by water can reach nanometer level. The metal oxides have certain spectral endothermic properties, and absorbable light can accelerate the melting of the coatings at elevated surface temperature.