Research on the Influence of Frequent Short-Circuit Grounding on the Insulation Characteristics of XLPE Material

In lightning-prone regions, the insulation performance of XLPE submarine cables under frequent reclosing behaviors critically affects cross-sea power transmission reliability. This study employs a frequent short-circuit grounding system to simulate stress and explore the relationship between electrical properties and aggregation structure. XLPE samples (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$200 \mu ~\mathrm{m}$</tex>) were aged at 80° C under operational (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$18 \text{kV} / \text{mm}$</tex>) and threshold (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$40 \text{kV} / \text{mm}$</tex>) electrical fields. Experimental results show that exposure to 80° C alone accelerates charge release but significantly reduces thermal stability (56.1 % drop in decomposition temperature). Aging under 3.6 kV causes slight charge accumulation and enhances crosslinking, partially recovering thermal stability (45.5 % drop). In contrast, 8 kV stress intensifies trap formation and structural defects, delaying charge dissipation and lowering decomposition temperature by 46.97 %. Although higher fields improve crystallinity through side-chain rearrangement, this does not enhance backbone stability. The results reveal the asymmetric impact of electro-thermal aging on XLPE's physical and chemical properties, offering insights for enhancing HVDC submarine cable reliability under transient stresses.