The reliability of polypropylene insulated cables depends not only on the performance of the cable insulation material itself but also on the extrusion molding process. To address the issue of the structural and performance changes in ethylene copolymerized polypropylene insulation before and after extrusion

the tests and characterization of multi-layered structure in power cable insulation were conducted

and the structure evolution of insulated state of multiphase polypropylene before and after extrusion and its effects on the electrical performance were analyzed. Results indicate that multiphase polypropylene insulation is highly sensitive to extrusion molding processes

and inconsistent microstructure is an important factor leading to a decrease in the insulation performance of polypropylene cables. After cable extrusion

the polypropylene molecular chains break

the crystallization ability decreases

and the shape of the dispersed phase becomes irregular and the size increases

resulting in a reorganization of the core-shell structure in the dispersed phase. Microscopic changes cause a decrease in trap energy levels and density

resulting in a significant decrease in the insulation performance of polypropylene under high temperature and high electric field. This result can provide guidance for polypropylene insulated cable extrusion processing.