To improve the efficiency and accuracy of cable ageing assessment, a new method based on residual antioxidant (AO) content is proposed. Cross-linked polyethylene (XLPE) cable insulation is thermally aged in laboratory at 110, 130 and 140°C from 240 h to 3600 h. The ageing degree of XLPE is characterized by tensile testing, AC breakdown measurement, and Fourier transform infrared spectroscopy. The residual AO content in XLPE is detected by FTIR as well as by oxidation induction time (OIT) measurement. It is observed that residual AO content measured by FTIR decreases monotonously with ageing time while OIT shows a non-monotonic transition. The results demonstrate that thermal deterioration is closely related to residual AO content and a critical value of residual AO content exists. During early stage of thermal ageing, the residual AO content is larger than the critical value and the variation in XLPE properties is relatively small. When the residual AO content decreases below the critical value, significant deterioration occurs. The close relationship between thermal degradation and residual AO content was analyzed by oxidative chain reactions.

中文翻译：

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通过残留抗氧化剂含量评估 XLPE 电缆绝缘层的老化

为了提高电缆老化评估的效率和准确性，提出了一种基于残余抗氧化剂（AO）含量的新方法。交联聚乙烯 (XLPE) 电缆绝缘材料在实验室中在 110、130 和 140°C 下从 240 小时到 3600 小时进行热老化。交联聚乙烯的老化程度通过拉伸试验、交流击穿测量和傅里叶变换红外光谱表征。XLPE 中残留的 AO 含量通过 FTIR 以及氧化诱导时间 (OIT) 测量来检测。观察到通过 FTIR 测量的残留 AO 含量随老化时间单调下降，而 OIT 显示非单调转变。结果表明，热劣化与残留AO含量密切相关，残留AO含量存在临界值。在热老化的早期，残留AO含量大于临界值，XLPE性能变化相对较小。当残留 AO 含量降低到临界值以下时，就会发生显着恶化。通过氧化链反应分析了热降解与残留 AO 含量之间的密切关系。