Dynamic ageing process of cross-linked polyethylene (XLPE) cable insulation under combined electro-thermal effect is investigated by the construction of theoretical analysis model and the practice of operation-simulated ageing test. Firstly, theoretical analysis model is constructed from time and spatial dimensions. From the time dimension, in the light of the impeding trend of internal stress to external stress, the XLPE ageing process of Steady state -Transition state -Steady state (STS) is proposed to illustrate the dynamic ageing process of XLPE. From the spatial dimension, the insulation is divided into three scales to quantify the ageing. Secondly, to practice the theoretical analysis model, an operation-simulated ageing test was conducted on two high voltage alternating current cables with service years of 15 and 30 for 540 days. Subsequently, relevant diagnostic measurements were applied to analyse the influence of physicochemical characteristics on the dielectric and heat transfer performances of the cables. The results show that the degradation of the actual operating cable is an extremely slow process. On the one hand, the response in physical changes of morphology counterbalances the external stress, maintaining the stability. On the other hand, once the chemical changes occur, negative feedback mechanism tends to impede the occurrence of further degradation by regulating fields distribution.

中文翻译：

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电热联合效应下基于时空维度的交联聚乙烯电缆绝缘动态老化研究

通过建立理论分析模型和运行模拟老化试验实践，研究了交联聚乙烯（XLPE）电缆绝缘在电热联合作用下的动态老化过程。首先，从时间和空间维度构建理论分析模型。从时间维度上，针对内应力对外应力的阻碍趋势，提出稳态-过渡态-稳态（STS）的XLPE老化过程来说明XLPE的动态老化过程。从空间维度上，将绝缘材料分为三个尺度来量化老化程度。其次，为了实践理论分析模型，对两条使用年限分别为15年和30年的高压交流电缆进行了540天的模拟运行老化试验。随后，应用相关的诊断测量来分析物理化学特性对电缆介电和传热性能的影响。结果表明，实际运行电缆的退化是一个极其缓慢的过程。一方面，形态物理变化的反应抵消了外部压力，保持了稳定性。另一方面，一旦发生化学变化，负反馈机制往往会通过调节场分布来阻止进一步降解的发生。