Effect of Crystalline Morphology on Electrical Tree Growth Characteristics of PP Insulation

Polypropylene (PP) insulation material displays higher melting point, high breakdown strength and volume resistivity, which meets the needs of high voltage cable insulation in the future. This paper focuses on the influence of crystallization characteristics on the resistant performance of electrical tree of polypropylene (PP). The sample of PP insulation are non-isothermally crystallized at different cooling rate and isothermally crystallized at different temperatures. The spherulite size of PP insulation samples decrease with the increase of cooling rate. The electrical tree of the sample cooled with a rate of 10 K/min has short trunks and many branches. While as the cooling rate slowed down and the spherulite size increased, the electrical tree branches decreased, the length increased, and the electrical tree deterioration increased. It is found that the electric tree tends to grow along the spherical crystal boundary.