固体绝缘沿面缺陷下的SF6分解特性及机理

Decomposition Characteristics and Mechanism of SF6 Under Surface Defect on Solid Insulator

为了奠定气体产物检测法在固体绝缘沿面缺陷诊断中的应用基础,在实验室内的SF6放电分解实验平台上探究了SF6气体在固体绝缘沿面缺陷下的分解特性,同时利用量子化学计算方法对关键产物的生成路径进行了研究。结果显示,固体绝缘沿面缺陷下的特征产物主要包括SOF2、SO2两种含硫含氧产物以及CO、CO2、CF4、CS2等多种含碳产物。其中CO2、CO、CS2的体积分数在放电最后阶段分别从0.46×10-6、4.22×10-6、18.69×10-6快速增长至2.05×10-6、14.76×10-6、27.77×10-6,可以认为其生成速率是判断缺陷严重程度的重要表征量。固体绝缘表面发生沿面放电时会发生复杂的反应,CF4主要通过碳氢化合物CHx逐步与F、HF反应生成;CO来源于碳氢化合物的氧化脱氢反应;CO2的生成则包括碳氟化合物氧化、CO氧化分解、碳氢化合物氧化脱氢等3个路径;CS2可能经CHx与S2或H2S反应生成。现场故障案例验证了该研究结论在实际生产应用中的实用价值。

In order to lay a foundation for application of gas analysis method in diagnosing surface defect on the solid insulation,we constructed an experimental platform to study the decomposition characteristic of SF6 under surface defect. Besides, the calculation method of quantum chemistry was adopted to explore the formation path of several kinds of key products. Experimental results show that main characteristic products under surface defect on the solid insulator include two kinds of sulfur-containing products and four kinds of carbon-containing products： SOF2, SO2, CO, CO2, CF4, and CS2. Contents of CO2, CO, and CS2 grow rapidly from 0.46×10-6, 4.22×10-6, and 18.69×10-6 to 2.05×10-6, 14.76×10-6, and 27.77×10-6, respectively. Therefore, it can be assumed that their formation rates are important characteristic parameters for determining defect severity. Complex chemical reactions happen when surface discharges occur on the solid insulator. CF4 is mainly derived from the reactions between carbureted hydrogen, F, and HF. CO is derived from oxidative dehydrogenation of carbureted hydrogen. CO2 is generated through various ways including oxidation of fluorocarbon, oxidative decomposition of CO, and oxidative dehydrogenation of carbureted hydrogen. CS2 is generated be the reaction between CHx and S2 or CHx and H2S. The fault cases prove the practical value of the research results in actual production.