机械应力对硅橡胶高压电缆附件运行可靠性的影响

Influence of Mechanical Stress on the Operation Reliability of Silicone Rubber High Voltage Cable Accessories

近年来由于高压电缆附件产品（终端与接头）的加工制作、安装施工不当等原因而引发了多起电缆线路故障,导致了爆炸、火灾等,造成了严重的经济损失,并给电网的安全运行带来了极大的风险隐患。为此,针对近年国内发生的多起重大的、具有共性特点的高压电缆附件工程热点故障案例,对故障及非故障接头进行了电树枝观测、材料性能试验以及电场、力学仿真计算,剖析了多起故障发生的共性原因及机械应力对高压电缆附件长期运行可靠性的重要影响作用。研究结果表明：电缆附件预制件承受的机械应力过大时将致使其环向机械应力增加,极端情况下可能导致电缆附件绝缘介质内部发生结构损伤和破坏,即使在较低电场强度下也可诱发电树枝,最终导致电缆附件绝缘介质本体击穿;而电缆附件预制件承受的机械应力较小时,会导致电缆附件预制件与电缆绝缘表面界面压力过小,进而会在界面处产生微小气隙等缺陷,引发界面放电。该分析结果可为后续硅橡胶高压电缆附件结构选型优化、试验检测以及安装质量控制等技术研究和工程实施提供借鉴。

In recent years, failures of several cable accessories have happened in China due to improper manufacturing and processing or installating. These failures have led to explosion, fire and resulted in great power loss and a big risk to the safe operation of power system. In order to analyze the reasons of the breakdown, we analyzed several failure cases of engineering hotspot high voltage cable accessories with common features. Numerous investigations were carried out by using the techniques of electrical trees observation, mechanical testing, and electrical and mechanical simulation. Finally we analyzed the causes of the failures and the important influence of the mechanical stress on the long-term operation reliability of the high voltage cable accessories. The study results show that the excessively high mechanical stress of cable accessories will greatly increase the cyclic tensile force, under the extreme case, will probably lead to some internal damage to the dielectric material of the stress cone and trigger electrical trees under a lower electrical field. However, the low mechanical stress will make the interface pressure between the cable and accessory also small.thus there will be some micro-cracks or other defects generated in the interface, which may lead to surface discharge. The results of the analysis can provide a reference for the technical research and project implementation of the follow-up selection and optimization of the structure, testing and installation quality control of silicon rubber high voltage cable accessories.