微水微氧对PD下SF_6分解特征组分比值的影响规律

Influence of Oxygen and Moisture on Feature Concentration Ratios of SF_6 Decomposition Products Under Partial Discharge

当SF6气体绝缘设备(gas insulated switchgear,GIS)内部存在绝缘缺陷时,往往会诱发不同形式的局部放电(partial discharge,PD),并导致SF6气体发生分解,然而其分解组分含量不仅与PD类型有关,还会受到放电气室内存在的微水微氧影响,如果选用分解特征组分含量或比值来识别PD类型,需对微水微氧的影响程度进行校正,以确保识别PD的准确率。为此,在分析PD使SF6分解机制的基础上,结合化学反应动力学理论,推导出适用于描述微水微氧含量对3组特征组分比值(即c(SO2F2)/c(SOF2)、c(CF4)/c(CO2)和c(CF4+CO2)/c(SO2F2+SOF2))影响规律的通用幂函数表达式,在建立的模拟针板PD下SF6分解实验平台上进行了大量实验,获得了不同微水微氧含量下4种稳定特征组分CF4、CO2、SO2F2、SOF2含量和3组特征组分比值的实验数据,利用最小二乘回归法确定出幂函数表达式中3个未知常数,最后用模型计算值与实测数据进行比较,结果表明理论预测能较好地反映微水微氧含量对3组特征组分比值影响的变化规律。

The concentration values of the SF6 decomposition products, generated by partial discharge （PD） in a gas-insulated switchgear（GIS）, are not only related to the type of PD, but also affected by the oxygen and moisture contents in the gas chamber. Therefore, the values of SF6 decomposition products or the three concentration ratios, which have been chosen as feature parameters in PD recognition, must be calibrated by the influence rules of oxygen and moisture on feature concentration ratios to enhance the performance of PD recognition. Combining SF6 decomposition mechanism with chemical dynamic theory, it is deduced that power function can express the influence law of oxwen andmoisture contents on the concentration ratios, namely, c（S02F2）/c（SOF2）, c（CF4）/c（C02） and c（CF4＋CO2）/c（SO2F2＋ SOF2）. In the current paper, needle-plate defect model was constructed and plenty of SF6 decomposition experiment was carried out to obtain the concentration data of CF4, CO2, SO2F2, SOF2 and three concentration ratios under different moisture content and oxygen content levels. Then the experiment data was delt with the nonlinear regression to confirm the unknown constants in the power function. Finally, compared the theoretical value with the experimental value, the results show that the theoretical prediction can express the influence rules of oxygen and moisture contents on the concentration ratios well.