500 kV SF6电流互感器电容屏缺陷下的 气体分解特性
Gas Decomposition Characteristics under Capacitive Screen Defect in SF6 Current Transformer

为了研究SF6电流互感器(CT)内存在电容屏缺陷时的气体放电分解特性,分别在实验室内的模拟平台和500 kV实体CT内开展了试验研究。在实验室模拟罐体内建立了场强方向平行于电容屏表面的缺陷模型1#和垂直于其表面的缺陷模型2#,在保持相同放电量的条件下对两种模型进行了SF6气体放电分解试验,结果显示:两种电容屏缺陷下的典型气体分解产物包括CF4、SO2F2、CS2、SO2和S2OF105种;在相同时间下,3种含硫氧化物的体积分数从大到小依次为φ(SO2)、φ(S2OF10)、φ(SO2F2),产物浓度随加压时间均呈现近线性增长趋势;CF4和CS2是涉及绝缘材料放电特有的分解产物,前者浓度远高于后者;对绝缘材料进行XPS元素能谱分析,得出C元素来源于绝缘材料;此外,放电量相近时模型2#下的分解产物浓度低于模型1#。最后,在500 kV SF6式实体CT内设置了电容屏沿面及屏间短路复合缺陷,结果表明,实体缺陷下的分解产物种类和变化趋势与同类型的实验室模拟缺陷结果一致。在实验室内模拟缺陷进行气体分解特性的研究对实际应用具有指导意义。
To reveal the gas decomposition characteristics under capacitive screen defects in SF6 current transformer, experiments were respectively carried out in laboratory platform and for 500 kV CT samples. Two discharge models of capacitive screen defects with the electric field parallel or perpendicular to the insulator surface were established in the laboratory platform. The results show that SF6 decomposition products include CF4, SO2F2, CS2, SO2 and S2OF10, and the concentrations of SO2, S2OF10 and SO2F2 decrease in turn. And their concentrations rise nearly linearly with time. CF4 and CS2 are typical decomposition products under the discharge involving insulators and the concentration of the former is much higher than that of the latter. The XPS analysis indicates that C element is derived from the insulating materials. With the same discharge quantity, the decomposition products concentrations of model 2# are significantly less than that of model 1#. The compound defects including creeping discharge and interturn short circuit of capacitance screen were set in a 500 kV CT, and it is found that the type and changing trend of decomposition products coincide with the results obtained in laboratory platform