Brittle fracture in nonceramic insulators: electrical aspects of microscopic flaws in glass reinforced plastic (GRP) rods

Glass Reinforced Plastic (GRP) rods used in Non-Ceramic Insulators (NCI) were examined for microscopic defects in order to evaluate their role in causing brittle fracture. The rods evaluated utilized different types of glass fibers and resin systems. Niemeyer's generalized approach to Partial Discharge (PD) modeling was used to investigate the development of electrical discharges inside the rods. The results indicated that the PD inception voltage was well above the highest system voltage used presently. Thus, it was concluded that the reactive species required for the formation of acids could not be developed inside the rod. The results also suggest that chemical reactions other than acid production can promote stress corrosion cracking of the rod and these may play a significant role in the failure process.