Influence of Pressboard Orientation in the Electric Field on Lightning Impulse Discharge Characteristics of Oil-Pressboard Insulation

In recent years, due to the high concentration of solid particles in transformer insulating oil, some large power transformers domestic and abroad have caused insulation fault. The influence of metal particles on the breakdown voltage of transformer oil is self-evident, relevant research shows that the damage of metal particles to the insulation performance of transformer oil is much higher than that of non-metallic particles such as cellulose particles. In this paper, a discharge test tank was designed and manufactured, and a lightning impulse discharge test platform for oil-paper insulation was built based on shadow imaging principle. The preparation method of insulating oil sample containing fixed metal particle concentration was put forward, a streamer development characteristic test scheme had been worked out. The effect of copper particles on the discharge characteristics of oil-impregnated insulating paper under two different field arrangement was studied. Discharge streamer imaging experiments of two insulating paper models were carried out under pre-breakdown voltage, and the streamer morphology characteristics were compared with the pure oil gap. When the insulating paper is placed along field lines, the streamer tends to develop along the surface of the insulating paper as a whole, and the insulating paper will speed up the development of streamer in oil. When the insulating paper is placed perpendicular to field lines, the paper will not affect the development of the streamer between the oil gaps, but will prevent the final formation of the main discharge channel of the streamer.