Interfacial aging in composite insulators as a result of partial discharge activity

High voltage outdoor composite insulators used on transmission lines can be subject to degradation due to electrical discharge activity at the core-sheath interface. A methodology is described to explore the effect of de-bonding or loss of adhesion between the sheath and core in composite insulators. The use of planar geometry materials allows interfacial pressure to be varied and facilitates physical and optical imaging of the tracking as it grows and chemical analysis of the samples after aging. The associated electrode geometry allowed the tracking to develop in a constant field, unaffected by the earth electrode. Low pressure between the materials accelerated the growth the tracks. A correlation between partial discharge magnitude and track development is identified. Electrical tree growth was also observed penetrating the epoxy resin, initiated from the interfacial tracks.