硅橡胶热老化特性及其对电缆附件运行可靠性的影响

Thermo characteristics of Silicone rubber and its effects on operational reliability of extra-high voltage cable accessories

电力电缆大力发展,使得新型硅橡胶绝缘材料由于其优良的机电热性能得以广泛应用在超高压电缆附件绝缘领域,但是绝缘故障时有发生,成为电缆输电线路的薄弱环节。本文提出材料老化特性是影响超高压电力电缆附件运行可靠性的重要因素,对硅橡胶材料电树老化性能进行了深入研究,研究温度对电树起始电压、形态的影响规律和电树随着时间的发展规律。研究显示硅橡胶电树起始电压随温度的升高明显下降,电树形态从树枝状、松枝状向丛状树枝过渡,表明硅橡胶绝缘材料在电缆运行温度范围内存在明显的热破坏特性,对硅橡胶电缆附件绝缘可靠性造成不利的影响,而较高温度的丛状电树的滞长特性则将成为电缆附件的长期性故障隐患。在特性研究的基础上,对比分析了温度对硅橡胶和聚乙烯电树老化性能的差异,认为当前硅橡胶电缆附件故障频发的主要原因之一是对硅橡胶老化特性缺乏了解,造成现有的常规结构设计上冗余不足。

With fast development of power cable,Silicone rubber （SIR）,as an advanced internal insulating material,has been widely used in high voltage cable accessories due to its excellent insulation and mechanical performance,but there is still a lot of insulation failure.It was reported that material aging properties are main reason which influences the operational reliability of extra-high voltage cable accessories.In this paper,electrical tree aging characteristics was analyzed including the effects of temperature on electrical tree initiation voltage and tree shape in SIR.It was found that the electrical tree initiation voltage was declined badly with the temperature rise.And electrical tree shape transits from the branch tree and pine tree to bush tree.It was shown that there is thermo destruction under cable operating temperature which causes bad influence on cable operational reliability.Long hysteresis characteristics of bush tree in SIR may become hidden danger of long-term operating cable accessories.The difference of PE and SIR in temperature characteristics was discussed.It was considered that thermo destruction is the main reason of the problem above and the lacking understand of SIR aging characteristics is the main reason of frequent failure in high voltage cable accessories which causes insufficient allowance of architectural design of cable accessories..