多应力下电缆附件界面的绝缘老化及修复填充物的作用机理研究

Faults usually occur in urban power grids for cable accessories aging, but present solutions are simple and passive for the faults. The previous rejuvenation achievements mainly focus on water-tree rejuvenation in cable insulation. These researches are still not involved in filling in micro defects and their further mechanisms of action in insulation interfaces for cable accessories. Interface unit models and actual cable accessories are used for the research objects in the proposal. Electrical performances of insulation interface, including breakdown voltage, trap level, polarization-relaxation characteristics, electrical treeing initiation and partial discharge characteristics, are investigated under single and combined stresses with thermal, electrical and environmental stresses. The micro structure of interface and migration characteristics of silicone grease is also investigated in the insulation interface under the single and combined stresses. The relationships among them are studied to understand early degradation mechanism in the interface. A new silane coupling agent and phenolic antioxidants are used to produce the hydrolysis-condensation reaction and chemical bond in the interface. Based on these researches, it is achieved that the relationship among rejuvenation fluid components, micro-structure of interface and electrical performance. The effects of rejuvenation conditions are also investigated on micro structures and electrical performances for rejuvenated samples. The long-term mechanism of action of rejuvenation fillers is obtained in the interface cavities under effects of multiple stresses. This research is expected to reveal aging and rejuvenation mechanisms of cable accessories under multiple stresses.

针对城市电网中出现的大规模电缆附件老化所导致的频繁故障，现有解决手段单一而被动。过去的绝缘修复主要关注对电缆本体的水树进行绝缘修复，对于电缆附件的绝缘界面处存在的微观缺陷进行修复填充以及填充物的深层作用机理尚未涉及。本项目拟以界面单元模型和实际电缆附件为研究对象，研究它们在温度、电场及环境湿度等单一或多应力作用下其绝缘界面的介电性能（击穿电压、陷阱能级、极化-松弛特性、电树引发和局放特征等）、微观结构（物理和化学结构）、填充小分子迁移特性及它们间的关联规律，阐明其早期老化机理。采用新的硅烷偶联剂和酚类抗氧剂对绝缘界面的空腔进行水解-缩合并与基体形成化学键结合，以建立修复液成分、界面微观结构变化、修复后的介电性能三者之间的关联机制，探究修复条件对修复后样本微观结构和介电性能的影响规律。在复合应力作用下，研究修复填充物对界面空腔的长期作用机理。项目将揭示电缆附件在多应力作用下的老化和修复机理。

电缆附件是电缆系统的薄弱环节，面对电缆附件大规模老化所引发的频繁故障，现有解决手段单一而被动。过去的电缆绝缘修复主要针对本体的水树老化，对电缆附件界面绝缘的修复效果及作用机制尚未涉及。本项目研究了电缆附件绝缘界面在复合应力作用下的早期劣化机理；研究了电缆本体及接头的绝缘诊断及缺陷定位方法；研究了基于硅烷偶联剂水解-缩合的界面空腔填充修复机理及长效作用机制。主要成果包括：明确了温度循环对电缆附件界面压力及局部放电发展的作用规律，建立了界面小分子迁移-微观表面形貌-宏观介电行为关联机制；提出了包括Debye模型三支路参数和绝缘评估图谱的电缆老化多维度诊断判据，提出了通过脱陷电流计算陷阱能级及分布的方法；提出了基于频域反射法的电缆缺陷定位方法，并基于此进一步提出了电缆缺陷类型识别、中间接头定位的方法，实现了中间接头的受潮及劣化诊断；阐明了硅烷偶联剂水解-缩合修复产物对绝缘界面微观结构、介电特性的作用机理，建立了界面修复反应-微观结构-电气性能三者间的关联机制；提出了基于压力注入的电缆中间接头修复方法，揭示了修复条件对修复液 扩散及界面绝缘性能影响规律；提出了基于锚固反应的修复液与绝缘界面的固载方法，揭示了界面绝缘修复的长效作用机制。该项目研究成果发展了电缆附件绝缘老化、诊断和修复理论，并已在多家供电企业进行试点应用，部分成果已成功转化落地，为解决城市电网大规模的电缆系统老化问题提供了新的解决思路。