The insulation characteristics and decomposition components of C4F7N/N2 gas mixture, a potential substitute for SF6, were first explored by breakdown experiments/gas chromatography–mass spectrometer. The structural properties of C4F7N molecule and the decomposition mechanism of C4F7N/N2 gas mixture were analyzed based on the density functional theory calculation and ReaxFF molecular dynamics simulation. We found that C4F7N/N2 mixture has great self-recovery performance. The decomposition of C4F7N in a discharge mainly produces CF4, C2F6, C3F8, CF3CN, C2F4, C3F6, and C2F5CN, among which the relative content of C2F6, CF4, and CF3CN is higher. ReaxFF-MD simulations show that CF3, CN, F, and C3F7 are the four main free radicals produced by C4F7N. The decomposition characteristics of N2 are better than that of C4F7N. The addition of N2 has a certain buffering effect to avoid the massive decomposition of C4F7N. The global warming potential value of a gas mixture containing 20% C4F7N decreased by 94.32% compared with SF6. Relevant results not only reveal the decomposition characteristics of C4F7N/N2 mixture in a discharge comprehensively, but also provide a reference for engineering application and emission of a C4F7N/N2 gas mixture.

C 5 F 10 O (C5 perfluorinatedketone) has received extensive attention due to its great insulation and eco-friendly performance, which has the potential to replace SF 6 usage in power industries. In this paper, the power-frequency breakdown properties and discharge decomposition characteristics of C 5 F 10 O/Air and C 5 F 10 O/N 2 gas mixtures are explored. It is found that the AC breakdown voltage of the C 5 F 10 O gas mixtures increases gradually with both the gas pressure and the content of C 5 F 10 O. As the partial pressure of C 5 F 10 O increases, the relative insulation strength increasing trend of the C 5 F 10 O gas mixtures becomes less obvious with the increase in the gas pressure. The AC breakdown voltage of the C 5 F 10 O/Air gas mixture is higher than that of the C 5 F 10 O/N 2 gas mixture. In addition, the decomposition products of the C 5 F 10 O gas mixtures are mainly CF 4 , C 2 F 6 , C 3 F 8 , C 4 F 10 , and C 3 F 7 H. Under the same condition, the content of the CF 4 in C 5 F 10 O/Air gas mixture is higher than that of the C 5 F 10 O/N 2 gas mixture. The decomposition of the C 5 F 10 O/Air gas mixture after breakdown did not produce C 2 F 4 and C 3 F 6 . CF 2 O and CO 2 are not detected in the C 5 F 10 O/N 2 gas mixture. Moreover, the carbon precipitation on the electrodes' surface can be found for the C 5 F 10 O/N 2 gas mixture after 60 breakdown tests.INDEX TERMS C 5 F 10 O gas mixtures, AC breakdown, SF 6 alternative gas, decomposition component.

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H2S and CS2 can be quantitatively detected, as the decomposition components of insulating gas SF6.

The decomposition mechanism of an environmentally friendly insulating medium C3F7CN was explored.