# Environmental Effects on HV Dielectric Materials and Related Sensing Technologies
## 2 Analyses and Discussions
The key result of the study was that leakage current was more common for insulators during dry periods than humid ones. To minimize the effect of environmental effects on high-voltage insulating materials [43; 44], the surface of insulators was modified to ensure a long service life. Besides achieving a high stability and resistance to environmental pollutants, the insulators are required to have excellent electrical and mechanical characteristics to withstand the associated stresses present when they are installed in a power network. Improvements of ceramic insulators surfaces were proposed in [45]. Coated polymeric insulators capable of having a useful and longer life than uncoated insulators when exposed to contamination and moisture were proposed [46; 47; 48; 49; 50; 51] by maintaining a low leakage level, preventing dry band arching and minimizing water absorption, hence minimizing the risk of partial discharges or flashover. Improved insulators for icing and polluted environments were also proposed. [PERSON] proposed a one-part room-temperature-curable organopolysiloxane composition which is applied to the outer surface of an electrical insulator of glass or porcelain so that the electrical insulator may maintain its high insulating properties even in the presence of moisture, air pollution, ultraviolet radiation and other outdoor stresses [52]. A coating for achieving contamination-resistantinsulators was also proposed [53]. Exposure to sunlight and some artificial light can have adverse effects on the useful life of polymer coatings. UV radiation can break down the chemical bonds in a polymer. Since photodegradation generally involves sunlight, thermal oxidation takes place in parallel with photooxidation. The use of antioxidants during processing is not sufficient to eliminate the formation of photoactive chromospheres. UV stabilizers have been applied widely, and the mechanism of stabilization of UV stabilizers belongs to one or more of the following: (a) absorption/screening of UV radiation, (b) deactivation (quenching) of chromophoric excited states, (c) free radical scavengers, and (d) peroxididedecomposers. Methods of applying lotus-effect materials as a superhydrophobic protective coating for external electrical insulation system applications were proposed to prevent the attachment of water droplets which contain dust or other contaminants and to enhance the coating's UV stability [54]. Polymer insulators covered with a polydimethylsiloxane (PDMS) housing, which are replacing ceramic insulators, were investigated to assess their service life through an accelerated aging process [55]. In the study, working insulators with different ages were collected from service, and the changes in the mechanical and electrical properties and hydrophobicity of the PDMS cover against aging time were measured. The work indicated that the probable service life estimated from accelerated aging conditions under high-temperature and high-power UV radiation is substantially less than that obtained from natural aging. This conclusion is explained by complex environmental conditions where multiple factors not readily accountable for in laboratory experiments contribute in tandem to the accelerated aging. Methods and systems to clean the surface of insulator materials have been proposed [56] and are still used today on a scheduled basis, especially in the vicinity of the sea/ocean where dirt and salt can build up on the insulator surfaces. The cleaning is required as, when exposed to the moisture from dew, frost, or light rain, the dampened contaminants can conduct current and lead to partial discharge, flashover or the electrical failure of the insulator. Most insulator designs depend on wind and rain to clean the insulator surfaces, but, when natural cleaning is insufficient, other methods are required to clean the insulators. The cleaning systems usually use robotic arms and high-pressure systems to dispense cleaning liquids to clean and apply a silicon coating to improve the surface hydrophobicity.