Influence of pollution chemical components on AC flashover performance of various types of insulators

The pollution on insulators is composed of various chemical components, which threaten the stability of external insulation. However, the existing insulation designs have not taken this issue into consideration. This work aimed to study the influence of pollution chemical components on flashover performance of insulators with various materials. Flashover tests of porcelain, glass and silicone rubber insulators polluted by eight types of common contaminants were conducted. Based on the test data, the influence of chemical components and their solubility on equivalent salt deposit density (ESDD) and insulator flashover performance were analysed; and the electrical properties of different types of insulators were compared. Results show that the ESDD contribution rate changes with chemical components. The dissolution characteristic has a significant influence on the measurement of ESDD; slightly soluble contaminants need to be considered separately. The corresponding insulator flashover gradient for ions can be summarised as Cl- < NO3- < SO42-, K+ < Na+, NH4+ < Ca2+. For a glass insulator, the flashover gradient is 4.9-17.0% higher than that of a porcelain insulator. For a silicone rubber insulator, this gap reaches 14.6-24.4 and 83.3-90% for freely soluble pollution and CaSO4, respectively, this phenomenon can be explained by the combined action of the slightly soluble character of CaSO4 and hydrophobicity transference of silicone rubber.