硅橡胶绝缘高压电缆附件的老化特性研究

Research on Aging Characteristics of Silicone Rubber Insulated High Voltage Cable Accessories

为研究高压电缆附件绝缘在电、热和环境等多因素作用下的老化特性,文中以6种退役硅橡胶绝缘高压电缆附件样品为研究对象开展工作。采用SEM、FTIR和XRD分析了不同运行环境下样品的理化特性和微观分子结构变化,通过介电测试和表面电位衰减测试获得了样品宏观介电性能和微观电荷特性,采用拉伸实验获得了绝缘样品的力学性能数据,最后结合上述表征对电缆附件的绝缘和老化状态进行评估。结果表明硅橡胶附件老化过程中以Si-O主链降解为小分子为主,小分子物质进一步发生氧化和重结晶反应,导致分子的交联度下降和极性增强,同时微粒团簇形成应力集中点和放电通道,外在表现为力学性能下降和介电常数改变;硅橡胶绝缘表面在电、热和应力作用下出现裂纹和孔洞,分子链断裂形成低密度区,影响材料表面的陷阱密度和能级深度,宏观体现为电缆附件绝缘击穿场强和电阻率的变化。

For studying the aging characteristics of the insulation of high-voltage cable accessories under the action of multiple such factors as electricity,heat and environment,6 kinds of silicone rubber high voltage cable accessories samples,which are out of operation,are taken as the research object and the corresponding work is developed.The SEM,FTIR and XRD are used to analyze the physical and chemical properties and micro-molecular structure changes of the samples under different operating environments.The macro-dielectric properties and micro-charge properties of the samples are obtained through the dielectric test and the surface potential attenuation test,and the mechanical performance data of the insulation samples is obtained by the tensile test.Finally,the insulation aging state of the cable accessories is assessed in combination with above characterization.The results show that in the aging process of SIR accessories,the main chain of Si-O is degraded into small molecules,and the small molecules undergo oxidation and recrystallization reactions further,resulting in a decrease in the degree of cross linking of the molecules and an increase in polarity.At the same time,the particle clusters form stress concentration points and discharge channel and the external manifestation is decrease in mechanical properties and a change in dielectric constant;cracks and porosity appear on the surface of the SIR insulation under the action of electricity,heat and stress,and molecular chain breaks to form low-density areas,which affect the density of traps and energy level depth on the surface of the material,macroscopical change of insulation breakdown field strength and resistivity of cable accessories.