Silicone-Oil-Based Repair Agent for Buffer Layer Ablation: Swelling Effects on Insulation Shields in High-Voltage Power Cables

In recent years, liquid-phase repair technology has been applied to mitigate buffer layer ablation faults in highvoltage power cables. However, the swelling mechanisms of repair agent on the cable insulation shields (CIS) remain unclear. This study systematically investigated the swelling effects induced by the silicone-oil-based repair agent on the CIS. Experimental results demonstrated: (1) Mechanical properties of CIS underwent rapid degradation during <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0-10$</tex> days of immersion, with tensile strength and elongation at fracture decreasing by 34.7% and 20% respectively, stabilizing after 30 days; (2) Mass loss followed a negative exponential decay pattern, reaching dynamic equilibrium at 30 days; (3) Volume resistivity exhibited non-monotonic variation, initially decreasing before gradual recovery; (4) Elemental analysis revealed continuous accumulation of silicon at cross-sections over immersion time, approaching saturation at 30 days, indicating material migration equilibrium during swelling. Finally, the swelling mechanism in the restorative agent-CIS system was elucidated through molecular diffusion kinetics and free volume theory.