冷缩式中间接头是配网电缆线路的性能薄弱部位，其运行、劣化特性直接影响电力系统的供电安全和稳定。硅橡胶绝缘运行于电、热、机械、环境因素等多应力耦合的复杂条件下，不同应力对电缆接头的单独、联合作用效果尚不清晰，电缆线路的性能提升遭遇瓶颈。本文对多应力作用下中间接头的运行和劣化特性进行研究，分析不同应力的影响效果和耦合机制，为提升配网电缆的运行能力提供理论和技术支撑。基于中间接头在运行状态下承受的机械应力，探究了机械拉伸对硅橡胶相对介电常数、交流击穿强度的影响特性，分析了填料含量、基体组成起到的作用效果；结合交联体系、力学性能表征，阐明了硅橡胶的微观拉伸机制及电气性能变化机理。研究发现，机械拉伸对硅橡胶的相对介电常数、交流击穿强度分别具有降低和强化效应，随伸长率增加，影响效果愈加显著，机械应力下分子链的取向伸直是其中的主要原因。搭建了热-机械拉伸联合劣化试验平台，开展了硅橡胶在热-机械拉伸作用下的加速劣化试验，分析了力学性能、电气性能和交联体系参数随伸长率、劣化时间的变化规律，总结了热、拉伸应力下硅橡胶的劣化机理和耦合机制。结果表明，热、拉伸应力对硅橡胶力学性能、硬度、体积电阻率的影响具有协同效应，对其交联密度、介电常数及损耗的影响存在竞争效应；硅橡胶的电导和界面极化行为在拉伸劣化下被显著促进，能够作为硅橡胶劣化状态的有效评价指标。搭建了配网电缆加速受潮试验平台，开展了电-热-水分等多因素作用下的电缆及接头受潮劣化试验，基于多性能联合检测的运行状态评估方法，对5类典型缺陷、9种运行条件下电缆及接头的受潮过程和电气性能变化规律进行了系统研究。中间接头受潮具有阶段性发展特征，多层界面结构是水分进入的主要途径，密封失效是电缆严重受潮的直接原因。基于湿热环境下中间接头的密封需求，提出了双层介质界面的气密性检测方法，结合不同界面压强、粗糙度下界面的微观接触状态，分析了气密性指标和绝缘性能参数之间的相关性，验证了气密性检测方法对于界面性能评价的可行性和有效性。
Cold shrinkable joints are the weak parts of the distribution cable lines, whose operation, degradation characteristics directly affect the supply safety and stability of power system. Silicone rubber operates in the complex conditions of electrical, thermal, mechanical, environmental factors and other multi-stress coupling. The separate and combined effects of different stresses on cable joints are not yet clear, which hinders the improvement of cable line performance, and to provide theoretical and technical support for the improvement of the operation capability of distribution cables.Based on the mechanical stress of cable joints under operation, the influence of mechanical stretching on the relative permittivity and AC breakdown strength was investigated, and the effect of filler content and matrix composition was analyzed. Combined with the crosslinking system and mechanical property characterization, the microscopic stretching mechanism and the mechanism of electrical property variations were illustrated. It is found that the mechanical stretching has decreasing and enhancing effects on the relative permittivity and AC breakdown strength of silicone rubber, respectively, and the effect is increasingly significant with the increase of elongation, in which the orientation straightening of molecular chains under mechanical stress is the major reason.A combined thermal-mechanical tensile degradation platform was established, and accelerated degradation test of silicone rubber under thermal-mechanical tensile effect was performed. The changing rules of mechanical properties, electrical properties and crosslinking system parameters with elongation and degradation time were analyzed, and the degradation mechanism and coupling mechanism of thermal and tensile stresses are summarized. The results show that thermal and tensile stresses have synergistic effects on mechanical properties and volume resistivity, and competitive effects on crosslink density and relative permittivity. The conductivity and interfacial polarization behaviors of silicone rubber are significantly promoted by tensile degradation, which can be an effective indicator for evaluating the degradation state.An accelerated moisture test platform for distribution cables was built, and moisture degradation test of cables and joints under multiple factors of electrical, thermal, moisture was carried out. Based on the operational state assessment method of multi-performance combined testing, the moisture ingress process and electrical performance changes of cables and joints under 5 types of typical defects and 9 kinds of operational conditions were systematically studied. The moisture ingress in cable joints is characterized by staged development, the multi-layer interface structure is the primary pathway for moisture ingress, and sealing failure is the direct cause of moisture in the joints.According to the sealing requirements of cable joints in hygrothermal environments, the airtightness detection method of double-layer medium interface is proposed. Combined with the interface contact state under different interface pressure and roughness, the correlation between airtightness indexes and insulation performance parameters was analyzed, and the feasibility and effectiveness of the airtightness testing method for interface performance evaluation were verified.
