Effective Equivalent Salt Deposit Density of polluted silicone rubber insulators in wetting process

The pollution flashover characteristics of insulators are tightly related to the salt dissolving out of pollution layer which makes contribution to surface conductivity of insulators in wetting process. For hydrophobic pollution layer on silicone rubber (SR) insulator, both the process of salt dissolving out and the process of salt running off are more complicated in wetting process. The concept of Effective Equivalent Salt Deposit Density (EESDD) is used to characterize the effective salt in wetting process, which is defined as the amount of salt dissolved in water on insulator surface minus the amount of salt ran off from insulator. Actual measurements indicate that EESDD of SR insulators increases in initial half of the wetting period and decreases in ending half of the wetting period. Hydrophobicity of pollution layer, NSDD, polluted manner all have significant influence on EESDD in wetting process. The wetting process of SR specimen keeps 6-9 times as long as that of glass specimen. For naturally polluted SR insulators, maximum percent of EESDD is about 15% of the total ESDD, which is another reason why SR insulators have higher pollution flashover voltage.