Measurements and analysis of surface damage on oil-impregnated insulation paper caused by partial discharge

Surface topography, surface roughness, and surface conductivity of oil-impregnated insulation paper were studied during the damage process caused by partial discharge within the cavity of the paper. Products generated on the surface during this process were studied, as well. According to phase-resolved partial discharge patterns, the damage process can be divided into five stages. At each of the stages, surface conditions of insulation were analyzed by optical microscopy, scanning electron microscopy, atomic force microscopy and high-resistance meter. 'Ablating', 'peeling', 'cracking in silk', 'pitting' and 'electrical treeing' appear on insulation surfaces one after another during the five stages of the damage process, along with sequential generation of droplets and crystalline solids. Surface roughness initially decreases, then increases. Finally, surface conductivity exhibits a general increasing trend, before it eventually stabilizes. However, its growth rate varies in different stages of damage.

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