Pollution tests for polymeric insulators made of hydrophobicity transfer materials

There are no standardized methods available at present for artificial pollution testing of polymeric insulators. Modified Salt Fog and Solid Layer tests based on procedures described in IEC 60507, intended for ceramic insulators, are thus often applied. Among methods evaluated for polymeric insulators made of hydrophobicity transfer materials (HTM), a modified Solid Layer test with preconditioning by dry powder is considered as being representative and most promising for future standardization. Further, the proposed procedure allows for testing at different hydrophobic states of the polluted insulators via the introduction of defined time between the application of pollution and voltage test. Finally, if the 50% flashover voltage is determined using e.g. the up-and-down method, results of the tests can be directly applied for insulator selection and dimensioning by means of statistical or deterministic methods.