Effect of oxygen on the thermal decomposition of eco-friendly gas insulating medium C4F7N-CO2

In recent years, C 4 F 7 N (fluorinated nitrile) is considered to be the most potential candidate gas for SF 6 in gas insulation equipment because of its excellent electrical performance and environmental protection advantages. However, there are few studies on the effect of O 2 on decomposition characteristics of C 4 F 7 N-CO 2 mixture. In this paper, we set up an experimental platform to simulate the thermal decomposition. We studied the effect of O 2 on the decomposition path of C 4 F 7 N-CO 2 mixture. The influence of pressure on the decomposition products of C 4 F 7 N-CO 2 mixture has also been studied. Gas chromatography-mass spectrometry (GC-MS) was used to detect the decomposition products. The experimental results show that the mixture of C 4 F 7 N-CO 2 decomposes into C 3 F 8 , CF 3 CN, C 3 F 6 , C 4 F 10 , C 2 F 5 CN and C 4 F 8 at an overheated temperature of 500 °C, and the mixture of C 4 F 7 N-CO 2 decomposes into C 3 F 8 , CF 3 CN, C 3 F 6 after adding O 2 . The addition of O 2 reduced the type of decomposition products and accelerated the decomposition rate of C 4 F 7 N-CO 2 mixture. The addition of O 2 should be avoided in the engineering application of C 4 F 7 N-CO 2 mixture. Increasing the pressure of C 4 F 7 N-CO 2 mixture in gas insulated equipment can effectively reduce the effect of O 2 on the decomposition of overheat.