Pollution tests for coastal conditions on an 800 kV composite bushing

The dry salt layer pollution test method is introduced as a better alternative to the present standardized insulator test method for coastal environments. Comparative tests were performed on an 800 kV composite housed SF₆ filled bushing, using the salt-fog and dry-salt-layer test methods. The two test methods are described and compared. Details of the external insulation of the 800 kV bushing are provided together with the results from the withstand tests performed. The discussion focuses on the mechanism of pollution deposit under each of the test methods and on the advantage that the dry salt layer method has when testing hydrophobic insulators.