Test method for evaluation of ability for recovery of hydrophobicity of composite insulators

A key feature for composite insulators is their ability for recover of hydrophobicity of the housing, which should be preferably kept during the whole service life. As long as a material is "alive" and produce the so-called Low Molecular Weight (LMW) components, encapsulating salts in the pollution layer, the in-service pollution performance will be good. At present there is no relevant tests to evaluate the recovery of hydrophobicity, only the so-called Hydrophobicity Transfer Test became recently available in IEC standards (2021). The test is purely intended to distinguish the Hydrophobicity Transfer Materials (HTM) from non-HTM, rather than to rank different HTMs. Thus, a new test, called Test of Recovery of Hydrophobicity (Dynamic Hydrophobicity Test) is proposed in this paper. Development of this test method is presented starting with the plates of materials and to the insulator's samples. The background for the test is as follows: LMW components governing the material's hydrophobicity penetrate the pollution layer and encapsulate the salt particles. This process gradually increases the electrical resistance of the pollution layer. The recovery ability can be evaluated and compared for different artificially contaminated insulators by measuring how the resistance of the pollution layer increases over time.