In Situ Formation of a SiO ₂ Transition Layer for Enhanced PP / SiR Interface Insulation in HVDC Cables

Charge accumulation and electric field distortion at heterogeneous interfaces critically affect the insulation reliability of high‐voltage direct current (HVDC) cable accessories. This study evaluates polypropylene (PP) as an environmentally friendly alternative to cross‐linked polyethylene (XLPE), emphasizing the electrical behavior at the PP/silicone rubber (SiR) interface. PP shows lower conductivity and higher tensile strength than XLPE, but suffers from interfacial charge accumulation and poor compatibility. To mitigate these issues, a SiO 2 transition layer was in situ grown on SiR via the TEOS sol–gel method. The modification increased surface density, introduced deep traps, and improved interfacial bonding, thereby suppressing carrier transport. At a TEOS:EtOH ratio of 1:6, the modified SiR achieved a breakdown strength of 141.77 kV/mm and an interfacial breakdown voltage of 20.87 kV, exceeding that of the XLPE/SiR interface. These results provide a theoretical and experimental basis for applying PP in HVDC cable accessories and optimizing composite insulation interfaces.