The Influence of Absorbed Moisture on Partial Discharge Patterns Measured During Tree Growth in an Epoxy Resin

Electrical treeing is a significant degradation mechanism in polymers that can lead to premature failure of high voltage equipment. This paper reports on an investigation into the relationship between the moisture content of epoxy resin samples and the phase resolved partial discharge activity measured during tree growth. The measured phase resolved partial discharge patterns showed a moisture dependent phase shift in the partial discharge activity relative the phase of the applied ac voltage. It was found that the conductivity increases with increasing the moisture content in the samples and the observed phase shifts in the partial discharge activity were attributed to increased electrical conductivity of the epoxy resin.