C_(4)F_(7)N/CO_(2)/O_(2)混合气体PD作用下气体和固体副产物生成特性

Gas and Solid By-product Generation Properties of C_(4)F_(7)N/CO_(2)/O_(2)Gas Mixture Under Partial Discharge

C_(4)F_(7)N/CO_(2)/O_(2)混合气体以其优异的环保和绝缘性能成为目前最具潜力替代SF6应用于电力工业的气体绝缘介质。尽管O_(2)的加入可以在一定程度上提升C_(4)F_(7)N/CO_(2)混合气体的绝缘性能和化学稳定性,但O_(2)加入及其体积分数变化对混合气体局部放电(partial discharge,PD)作用下气体和固体副产物生成特性的影响规律尚不清楚。因此通过针–板电极模拟设备内的金属突出物缺陷开展C_(4)F_(7)N/CO_(2)/O_(2)96 h PD及其分解特性试验。研究发现C_(4)F_(7)N/CO_(2)混合气体中加入体积分数2%~4%的O_(2)可以显著抑制大部分副产物的生成,O_(2)体积分数大于6%时每秒累积放电量和平均放电量急剧增加,导致混合气体分解加剧;C_(4)F_(7)N/CO_(2)/O_(2)在长时间PD作用下板电极表面中心区域出现较为明显的圆环状固体析出物,主要成分包括金属氧化物(CuO)、氟化物(CuF、CFx)、碳氧化合物(CO、CO_(2))和氮氧化合物(NO、NO_(2));体积分数4%的O_(2)加入对PD固体析出物的元素组成及其价态影响较小,但可以一定程度上减少其生成量,混合气体中O_(2)对金属导体的腐蚀作用弱于C_(4)F_(7)N。

C4F7N/CO_(2)/O_(2)gas mixture has become the most potential alternative to SF6 gas insulation medium in the power industry because of its excellent environmental protection and insulation properties.Although the addition of O_(2)can enhance the insulating properties and chemical stability of C4F7N/CO_(2)gas mixtures to a certain extent,the pattern of the influence of O_(2)addition and its change in volume fraction on the generation characteristics of gases and solid by-products under the action of PD of the gas mixtures is not clear.In this paper,experiments on C4F7N/CO_(2)/O_(2)96 h PD and its decomposition characteristics were carried out through metal protrusion defects in a pin-plate electrode simulation device.It is found that the addition of 2%~4%O_(2)to the C4F7N/CO_(2)gas mixture can significantly suppress the generation of most of the by-products,and the cumulative discharge per second and the average discharge per second will increase dramatically at O_(2)volume fractions greater than 6%,leading to increased decomposition of the gas mixture.C4F7N/CO_(2)/O_(2)shows obvious circular solid precipitates in the center area of the plate electrode surface under long-term PD action,and the main components include metal oxides(CuO),fluoride(CuF,CFx),carbon oxides(CO,CO_(2)),and nitrogen oxides(NO,NO_(2)).The addition of 4%O_(2)has a negligible effect on the elemental composition and valence state of PD solid precipitates,but can reduce its production to a certain extent.The corrosion effect of O_(2)on metal conductors in mixed gas is weaker than that of C4F7N.