The Morphology Development Law of Oil-paper Insulation White Mark with Different Moisture Content

Partial discharges in oil-paper insulation usually leads to the formation of white mark and have an effect on the insulation properties of the paperboard. In order to investigate the morphological characteristics of white mark during the growth phases and the effect on the insulation properties, experiments based on pinboard electrode model are carried out in this work. Through the white mark growth experiment of paperboard with different moisture content, the development process of oil-paper insulation white mark was observed and recorded by camera in real time. The results show that the white mark has two types of growth after initiation. The development process of type I is the initiation and growth of the white marks until the paperboard is breakdown, but the development process of type II shows the initiation, growth and disappearance of the white marks. The applied voltage is the main cause of this phenomenon.