Cross-linked polyethylene (XLPE) is widely used as an insulating material for power cables due to its excellent performance. XLPE insulation is manufactured through processes such as triple-layer co-extrusion

crosslinking

and degassing. With increasing demands for higher temperature resistance and voltage levels of XLPE

it is necessary to explore effective ways to further enhance its insulation performance without altering the raw materials. This study investigates the relationship between the microstructure

properties

and processing techniques of XLPE

revealing that different extrusion processing speeds lead to varying degrees of molecular chain orientation in XLPE insulation

thereby affecting its structure and performance. XLPE cables were fabricated at two different extrusion processing speeds (2 m/min and 3 m/min). The results show that increasing the extrusion processing speed raises the gel content from 74.9% to 81.1%

reduces the load elongation from 64.2% to 54.6%

decreases the average molecular weight between adjacent cross-linking points from 21 132 g/mol to 19 854 g/mol

and slightly increases crystallinity. The tensile strength of XLPE samples increases by 2.0 MPa

while the elongation at break decreases by 12.1%

and the oxidation induction time extends by 8.9 min. At 70 ℃

the DC conductivity decreases

the DC breakdown strength increases from 222.3 kV/mm to 252.4 kV/mm. The main reason for the changes in performance is that the extrusion processing speed affects the degree of molecular chain orientation in XLPE insulation and alters the packing structure of molecular chains

thereby causing differences in the crosslinking degree both between and within molecular chains. This leads to the spatially inhomogeneous distribution characteristics of the aggregated structure of XLPE

which in turn determines the variations in various macroscopic physical properties.