# Environmental Effects on HV Dielectric Materials and Related Sensing Technologies
## 2 Analyses and Discussions  
The degradation of the dielectric materials of HV insulators followed by their failure is an ongoing problem in the power network (PN). The main cause of insulator aging, degradation and failure is electrical discharge triggered by environmental factors and power overload. The major sources of environmental pollution include costal pollution, rain forest algae/moss, desert pollution, snow, lighting and industrial pollution. Among them, the most impactful factors are pollutants in coastal environments [7]. In these environments, temperature exposure, radiative exposure, relative humidity or moisture level, the counter-diffusion of hydroxide ions, the environmental load of salts and other adverse climate conditions play a key role in the degradation of insulating materials. The effect of various types of contamination deposition on insulator surface dry \begin{table}
\begin{tabular}{c c c} \hline \hline
**Nature of Suspended Matter** & **Diameter (\(\mu\)m)** \\ \hline \multirow{4}{*}{Inorganic} & Smoke & 0.001–0.3 \\  & Fumes & 0.01–1.0 \\  & Dust & 1.0–100.0 \\  & Bacteria & 1.0–10.0 \\ Organic & Plant spores & 10.0–20.0 \\  & Pollen & 15.0–50.0 \\  & Fog & 1.0–50.0 \\ Water & Mist & 10.0–100.0 \\  & Drizzle & 50.0–400.0 \\  & Rain & 400.0–4000.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The size range of typical pollution particles [5]. band arching [8] and flashover [9; 10; 11; 12; 13; 14; 15] indicated the effect of direct contamination on the performance of insulators. The effect of wind speed on the accumulation of pollution in HV insulators was also investigated [16; 17]. The high wind speed and direction are especially relevant along the ocean/sea shore, where the saline accumulation rate, diffusion and penetration rate and distance from the sea are closely related factors. Pollutants mainly comprise marine-specific soluble salts (NaCl and Na\({}_{2}\)SO\({}_{4}\)) dissolved in water droplets and carried by nano/micro bubbles. They lead to the development of a continuous water film and the distribution of pollution layers on the insulator surfaces, which can cover the surface of the insulators partially or totally. When the contaminated insulator surfaces become wet, some of these particles are dissolved, causing the insulator surfaces to become conductive [18; 19; 20; 21]. To that end, the effect of wind and distance from the seaside on the insulating surface contamination was investigated [22]. The effects of deposits of sandstorms and free carbon particles (soot) on the flashover activity of ceramic and polymeric insulators were also investigated [23]. The study indicated that the deposition rate of soot particles was highly increased when both porcelain and polymeric insulators were already polluted with sand particles, regardless of whether the sand particles were charged or not. The work also demonstrated that moisture was critical to pollutant layer build-up and increased the severity of pollution. The effect of the desert sandstorms on the reliability of the HV insulators was considered [24]. The work showed that long-time exposure of sand particles to electric fields results in charging the sand particles deposited on the surfaces of insulators, which in turn can support surface discharge. Sand particles, classified as non-soluble pollution sources, were indicated to decrease the reliability of power networks [25]. An investigation of the contamination of 1.4 mg/cm\({}^{2}\) sand particles in desert areas on ceramic insulators with a standard creepage distance of 31 mm/kV from phase to phase was performed [26]. The results indicated that this creepage distance is insufficient to withstand desert pollution. High-speed winds carrying sand in deserts are a major source of contamination for the HV insulators. This is also due to the fact that sand storms can cause insulator material erosion [27]. The hydrophobic stability of silicone rubber, which makes it suitable for these erosive conditions, is attributed to low molecular weight silicone components.