Accelerated aging of insulators under acid rain conditions

Various commercially available 15 kV class polymer distribution insulators were evaluated in addition to a traditional porcelain insulator under acid rain conditions to evaluate suitability in this environment. The polymer insulators had either silicone rubber (SR) or ethylene propylene diene monomer (EPDM) as shed materials. Continuous leakage current measurements were taken to characterize aging of the materials. The leakage current plots allowed identification of transitions in the conduction behavior, which were used to infer the existence of irreversible damage to the materials. To separate electrical and chemical aging effects, matching samples were used on the rotating tracking wheel. In another test, variable length rest periods were used to investigate the recovery rate from electrical and chemical stressing of the materials. It was found that the aging characteristics fell into distinct groups that were strongly dependent on the base material.