On the Chemical Composition and Hygroscopicity of Aerosols Deposited on the Insulators of Italian Power Lines

Featured Application: The results presented in this paper highlight the chemical nature of the deposits measured on high power line insulators in Italy; the results also underline the significant role of inorganic ions in forming a conductive layer on insulators when exposed to moisture, leading to the risk of flashover events. Applications are related to the prevention of such phenomena by identifying the phase transitions of atmospheric aerosols deposited on insulators and their associated conductive effect. This is achieved through the generation of synthetic aerosols and the study of their phase transitions and conductance in an aerosol exposure chamber (AEC). The reliability of the national power grid is a key issue in modern society. Atmospheric aerosols are the main cause of the reduction in the performance of insulators and the increase in the possibility of flashovers, resulting in power line failures. Under high ambient humidity, the water-soluble compounds of atmospheric aerosols collected on the insulators’ surface can dissociate in ions and form a conductive layer, which may lead to flashover events. With a view to investigating the processes that drive these phenomena, the chemical composition of aerosol deposits on insulators in Italy was determined by ion chromatography analysis and thermos-optical and X-ray techniques. In addition, a synthetic aerosol with the same analyzed chemical composition was generated in a laboratory and deposited on PTFE filters and glass specimens allowing us to determine the deliquescence and crystallization relative humidity and the conductive effect in an aerosol exposure chamber. The results evidenced the presence of a hazardous inorganic ion layer, which generates a sharp phase transition of the aerosol deposit as a function of the ambient relative humidity; this layer poses a dangerous threat to the reliability of the power grid, increasing the probability of flashover events where the conductive layer facilitates the flow of electrical current across the insulator surface, potentially causing power outages or damage to the power lines.