Heterogeneous mesoscopic structure modulation enhancing dielectric strength of polypropylene insulation

This paper focuses on the heterogeneous mesoscopic structure modulation enhancing dielectric strength of polypropylene insulation. α-nucleating agents are used to modulate the heterogeneous mesoscopic structure of polypropylene, and Voronoi Network models with similar structures are established to simulate the electric field distribution at the mesoscopic scale. The experimental results show that the addition of an α-nucleating agent effectively diminishes the spherocrystal size and increases its density. The high continuity and wide range electric field distortion caused by the too-large spherocrystal size and too-loose arrangement is thus suppressed. The improvement of electric field uniformity effectively inhibits the frequency and intensity of partial discharge. Compared with pure polypropylene, the partial discharge in polypropylene composite with α-nucleating agents at 0.1 wt% decreased by 2414 times, and its maximum amplitude decreased by 58.3%. The increase in the spherocrystal density also enhances its blocking effect on the electrical tree growth, and the length and width of it are reduced by 88.6% and 89.1%, respectively. The dispersive development of the electrical tree reduces the incidence of penetration channels along the electric field direction. The breakdown strength is therefore increased by approximately 20%. The simulation results demonstrate that the dielectric property difference between the crystal and amorphous regions within polypropylene at the mesoscopic scale is the main reason that triggers the electric field distortion at its interface and further leads to insulating degradation or even failure. In this study, heterogeneous mesoscopic structure modulation is proved to be an efficient means to enhance the dielectric strength of polypropylene insulation.