Effect of Oxygen and Temperature on Thermal Decomposition Characteristics of C4F7N/CO2/O2 Gas Mixture for MV Equipment

Perfluoroisobutyronitrile (C4F7N)/CO2/O2has been considered as a potential eco-friendly gas insulating medium to replace SF6due to its unique dielectric properties. Nowadays, few studies on the thermal stability and decomposition properties of C4F7N/CO2/O2gas mixture were reported, which needs to be evaluated comprehensively. Herein, for the first time, we explored the effect of oxygen and temperature on thermal decomposition characteristics of C4F7N/CO2/O2gas mixture. It was found that CF4, C3F8, C3F6, CO, COF2, CF3CN, C2F5CN and C2N2are the main by-products of C4F7N/CO2/O2gas mixture upon decomposition. The addition of 2%-10% O2in the C4F7N/CO2gas mixture yielded decreased of C3F6and C2N2while the increase of other by-products. The yields and effective formation rates of C3F8and COF2accelerated when the content of O2was higher than 8%. In terms of practical application, adding 4-6% O2to C4F7N/CO2gas mixture is appropriate and COF2, C2N2, C2F5CN can be used as the characteristic products to reflect the severity of partial overheating fault of C4F7N/CO2/O2gas insulated equipment.