Investigations on rain fog pollution test [of insulators]

In the solid layer test method, it is mentioned that warm or cold water may be used, instead of steam for wetting the pollution layer. So an attempt is made to perform the solid layer test with the wetting action obtained from tap water, called the rain fog test. An important aspect of this method is that the existing spraying system of the salt fog method is used for the development. This will simulate the actual conditions of the pollution layer wetted with slight rain or drizzle or mist. In the rain fog method, the insulator is coated with a pollution whose layer conductivity simulates the site condition and tap water fog is applied to the insulator to simulate the actual rain, dew or drizzle. The withstand capability of the insulator string is tested as specified in IEC 507, 1991. To standardize the rain fog test facility, two tests are conducted viz. wetting action test (layer conductance test) and reference test on a nine disc insulator string. These two tests are identical to the tests necessary to standardize the solid layer test facility as specified in IEC-507. The rain fog test is a combination of salt fog test as well as solid layer test facility