Influence of Micro-aerobic and Air Pressure on the Decomposition Characteristics of C4F7N/CO2/O2 Gas Mixtures Under Suspended Discharge

With the goal of "carbon peak, carbon neutralization" being proposed, SF6 alternative eco-friendly C4F7N/CO2 gas mixtures have attracted wide attention. In order to explore the decomposition characteristics of C4F7N/CO2/O2 gas mixtures with different micro-aerobic and air pressure under suspended discharge, a series of gas decomposition experiments were carried out. The decomposition products were qualitatively and quantitatively analyzed by GC-MS and GC-PDHID. The results show that, when the oxygen volume fraction is 0%~10% and the air pressure is 0.25~0.65 MPa, the main products are CF4, C2F6, C3F6, C3F8, CNCN and CF3CN. With the increase of oxygen volume fraction, the main decomposition products show a variation trend of "U" type. The decomposition inhibitory effect is most obvious with the oxygen volume fraction of 4%. The decomposition products of C4F7N/CO2/O2 gas mixtures are negatively correlated with the air pressure, and large molecules such as C3F6 and C3F8 are more difficult to produce at high air pressure than small molecules such as CF4 and C2F6. The C3F6/C3F8 ratio in the absence of oxygen and the C2F6/C3F6 ratio at 0.25 MPa remains basically unchanged, which is suitable for suspended discharge recognition in these two cases. When using component analysis methods for fault diagnosis of suspended discharge, the influence of oxygen volume fraction and air pressure must be considered and corrected. © 2021, High Voltage Engineering Editorial Department of CEPRI. All right reserved.