目前在电力行业中广泛应用的SF_6气体具有严重的温室效应,寻找一种绝缘性能优良的环保型替代气体成为研究热点。近年来,C_3F_7CN及其混合气体凭借出色的绝缘性能和环保特性得到了国内外学者的广泛关注。目前针对其放电分解机理的研究较少。首先,基于ReaxFF反应分子动力学方法和密度泛函理论,从微观层面模拟研究了C_3F_7CN/CO_2混合气体的分解机理。基于构建的C_3F_7CN/CO_2混合气体模型,研究了温度对C_3F_7CN分解过程的影响,分析了其可能的分解路径、产物类型及分布等。计算结果表明,C_3F_7CN在局部过热或放电等故障条件下分解容易产生CF_3-、C_3F_7-、 C-、CF_3CFCN-、CF_2-和F-等各类自由基,上述自由基复合将产生CF_4、C_2F_6、C_3F_8、CF_3CN、CO等产物。其次,利用气体绝缘试验平台和气相色谱质谱联用仪(gas chromatography mass spectrometer,GC-MS),试验分析了其多次击穿后的分解产物。试验结果表明,混合气体多次击穿后的主要分解产物是CF_4、C_2F_6、CF_3CN。这些产物分子均具有比较好的绝缘能力,保障了C_3F_7CN/CO_2混合气体的绝缘性能不被破环。相关结论为进一步探究C_3F_7CN/CO_2混合气体的绝缘特性及协同效应等课题提供理论依据和工程指导。
英文摘要:
Due to the serious greenhouse effect of SF_6 gas, which is currently widely used in the electrical power industry, it has become a common view that an environmental-friendly alternative candidate of excellent insulation performance should be found to replace SF_6. Recently, the C_3F_7CN and its mixture, which have a low global warming potential (GWP) and excellent insulation properties, have attracted wide attention from domestic and foreign scholars. There are few studies on its decomposition mechanism under discharge. In this paper, firstly based on the molecular dynamics method and the ReaxFF force field and the density functional theory, the decomposition mechanism of C_3F_7CN/CO_2 gas mixture was simulated from the micro level. Based on the constructed C_3F_7CN/CO_2 models, the effect of temperature on the decomposition process of C_3F_7CN was studied, and the possible decomposition paths, product types and distributions were analyzed. The results show that the decomposition of C_3F_7CN can easily generate various kinds of free radicals such as CF_3-, C_3F_7-, C-, CF_3CFCN-, CF_2, F- and so on under the conditions of local overheating or discharge, and further reactive combination of these free radicals will generate products such as CF_4, C_2F_6, C_3F_8, CF_3CN, CO and so on. Then, based on the gas insulation test platform and the gas chromatography mass spectrometer (GC-MS), the products after multiple breakdowns were analyzed. The test results show that the decomposition product are mainly CF_4, C_2F_6, CF_3CN.These molecules products have good insulation ability, which insure the insulation performance of C_3F_7CN/CO_2 gas mixture. The conclusions provide theoretical basis for further research of insulation properties and synergistic effect of C_3F_7CN/CO_2 gas mixture, and guide its practical engineering application.