The dielectric breakdown phenomenon of insulating materials under strong electric field has always been a key problem restricting the development of AC cables towards higher operating voltage levels. Most of the current research on the thickness effect of XLPE insulation breakdown remains on the summary of macroscopic experimental phenomena, and it is rare to start from the mesoscale, based on the differences in the microstructure of materials, to explain the originality of the thickness effect.First, the surface-treated XLPE samples were observed by scanning electron microscope (SEM) to obtain the average thickness of spherulites. On this basis, XLPE samples with different thicknesses (×3/5/10/20/50 times the spherulite size) were prepared, and AC breakdown tests were carried out on them. At the same time, combined with molecular dynamics simulation to carry out modeling calculation, the development path of the breakdown channel in the crystalline region and the amorphous region is determined, and the difficulty of the breakdown process under different thickness conditions is analyzed.The experimental results show that the breakdown strength of XLPE decreases with the increase of the spherulite multiple. The simulation results show that the larger the thickness of the material, the more defects in the amorphous region in the structure, so it is easier to form and develop the breakdown channel.This paper combines experiments and simulations, considers the differences in the microstructure of XLPE under different thickness conditions, and analyzes and explains the reason for the thickness effect in the breakdown process from the mesoscale.


 

mesoscale,Effect of thickness,AC breakdown strength,XLPE cable insulation