C_(4)F_(7)N-air混合气体在稍不均匀和极不均匀电场中的工频绝缘特性分析

Power Frequency Insulating Performance Analysis of C_(4)F_(7)N-air Gas Mixture Under Slightly and Extremely Uneven Electric Fields

近年来,作为SF_(6)有效替代气体之一,七氟异丁腈(C_(4)F_(7)N)因其优异的电气性能和物化特性而受到关注与讨论,然而由于C_(4)F_(7)N的液化温度较高,需要与低液化温度的缓冲气体并用。选择空气作为缓冲气体,在稍不均匀电场与极不均匀电场下,通过工频击穿实验研究气压、混合占比和电极间隙对C_(4)F_(7)N-air混合气体工频击穿电压的影响。结果发现:C_(4)F_(7)N-air混合气体在两个电场下的工频击穿电压随着电极间隙的增大而近似线性增加,在极不均匀电场下,出现明显“驼峰”效应,混合比为8%~16%的C_(4)F_(7)N-air混合气体工频击穿电压可达到同条件下SF_(6)的67%~86%。在稍不均匀电场下,8%C_(4)F_(7)N/92%air混合气体的绝缘强度约为同条件下SF_(6)的0.8倍。混合比为12%~16%的C_(4)F_(7)N-air混合气体具备与SF_(6)相等的工频绝缘强度。总结:与SF_(6)对比,C_(4)F_(7)N占比为8%~16%的C_(4)F_(7)N-air混合气体具备替代SF_(6)气体的潜力。

In recent years,perfluoroisobutyronitrile(C_(4)F_(7)N),one of the most promising alternative gases to SF_(6) gas,has been widely focused and studied due to its superior insulating performance and stable physical and chemical properties.However,due to its high liquefaction temperature,C_(4)F_(7)N must be used in conjunction with a buffer gas with a lower liquefaction temperature.Air is chosen as the buffer gas in this paper.Under the slightly and extremely uneven electric fields,the influence of the gas pressure,mixing ratio and electrode gap on the breakdown voltage of C_(4)F_(7)N-air gas mixture is studied through the power frequency breakdown test.It is found by the result that the power frequency breakdown voltages of the C_(4)F_(7)N-air gas mixture under two electric fields increases approximately linearly with the increase of the electrode gap.Under the extremely uneven electric field,there is an obvious‘hump’effect.Under the same condition,the power frequency breakdown voltage of C_(4)F_(7)N-air gas mixture with mixing ratio of 8%-16%can reach 67%to 86%that of SF_(6).Under the slightly uneven electric field,the insulation strength of the gas mixture with mixing ratio of 8%C_(4)F_(7)N and 92%air is approximately 0.8 times that of SF_(6) under the same con-dition.The C_(4)F_(7)N-air gas mixture with mixing ratio of 12%-16%is comparable to SF_(6) gas in power frequency insulation performance.