Analysis of AC and DC Withstand Electrical Performance of Cable Insulation Samples at Different Scales

In the development of polymer insulation materials, it is essential to conduct equivalent testing and analysis using samples of various structural sizes to validate the insulation performance of larger specimens. This paper focuses on polypropylene-insulated power cables, utilizing compressionmolded flat samples, model cable samples, and rotary samples to assess the AC and DC dielectric performance of insulation with different structural dimensions. Comparative analysis was conducted with cross-linked polyethylene (XLPE) insulated samples of the same size. The results indicate that, compared to XLPE insulation, polypropylene exhibits excellent short-term breakdown performance in compression-molded samples. However, after extrusion and cabling, the AC dielectric performance significantly differs from that of XLPE cables with the same structure, with polypropylene cables experiencing intrinsic breakdown. Additionally, multiple breakdown points were observed during DC tests. Analysis reveals that the size effect on AC breakdown of polypropylene is more stable than that of XLPE, and the trap characteristics of polypropylene insulation differ significantly from those of XLPE. Therefore, attention must be paid to impurity content and processing factors during the molding of polypropylene insulation. Various regulatory methods should be employed to support the modification and optimization of polypropylene-insulated power cables.