Adhesion test between fiberglass rod & housing in composite insulators

The central weakness revealed in the insulators investigated during this research was poor adhesion-likely the result of production deficiencies. A possible mechanism behind what occurred during service could be that, over time, air-filled voids between the fiberglass rod and the silicone rubber housing filled with moisture due to diffusion through the housing. This eventually led to a partially conductive layer in this interface into which HV potential was transferred from the live fitting along the insulator. The short-circuited path amplified electrical stress and initiated corona, whose impact generally starts by degrading local hydrophobicity. The final result was either erosion or puncture through the housing.