退役电缆附件微观结构与电荷特性研究

电缆附件是输电线路中最容易出现故障的薄弱环节,从微观结构和电荷特性方面入手,分析和探索退役电缆附件的失效行为和影响规律,是提高电力系统安全稳定运行的关键。该文研究对象取样于退役或故障电缆附件绝缘,通过对其表面化学组成和形貌的观测分析、材料陷阱参数的测量计算以及空间电荷的测试,分析老化作用下三者之间的相互影响关系。结果表明:三元乙丙橡胶(ethylene propylene diene monomer,EPDM)绝缘的电缆附件,其老化标志除了出现C—O、C=O结构外,还包括因终端填充硅油而引入的含Si基团及其比例的改变;而在硅橡胶(siliconerubber,Si R)绝缘的电缆附件中,Si—O—Si比例的下降是其严重劣化的标志;与EPDM相比,Si R浅陷阱能级和密度占据优势,其表面电位衰减和电荷消散速度明显更快,能够有效避免空间电荷的集聚,但是由于Si R较差的抗撕裂性容易产生裂纹;退役电缆附件长期运行在复杂的环境下,材料的氧化、主链和侧链的断裂及其他杂质的生成,是附件绝缘陷阱参数及电荷特性变化的主要原因。

Research on Microstructure and Charge Characteristics of Cable Accessories out of Service

The cable accessory is the weak link of insulation prone to failure in a transmission line. It is a key technology to improve the safe and stable operation of power system to analyze the failure behavior and effect mechanism of aged cable accessory from the aspects of microstructure and charge characteristics. The samples in this paper were obtained from retired EPDM and SiR insulated cable accessories. Then the surface chemical composition and morphology were observed and analyzed, and the trap parameters and space charge were measured and calculated. Finally, their interaction during the aging process was analyzed. The results show that the introduction of Si containing groups and the change of their proportions are important marks of EPDM aging besides the generation of C—O and C=O structures. In SiR insulated cable accessories, the decrease in Si—O—Si chemical bonds is an important mark of SiR degradation. Compared with EPDM, the trap energy level is shallower and the shallow trap density is higher for SiR. The surface potential decay and charge dissipation rate are obvious faster for SiR, which can effectively avoid the accumulation of space charge. However, SiR is prone to crack to introduce new defects due to its poor tear resistance. The main reasons for the change of trap parameters and charge characteristics of aged cable accessories are the oxidation of materials, the breaking of main and side chains and the formation of other impurities under the long-term and complex operating environment.