Surface discharge pattern of C4F7N/CO2 mixture under negative impulse voltages

Abstract

Due to the excellent properties, C4F7N/CO2 mixture is the most concerned eco-friendly SF6 alternative gas. For a better understanding of the surface discharge characteristics, the surface discharge pattern of C4F7N/CO2 mixture under negative impulse voltages is investigated in this work. The morphology of the surface discharge is obtained by an optical method and a dust figure method. The structure of the surface discharge is established, which from the outside to the inside consists of electron cloud, streamer, streamer stem, and leader. The propagation pattern of the surface discharge in C4F7N/CO2 mixture under negative impulse follows the stepwise expansion pattern. The structure of the surface discharge in C4F7N/CO2 mixtures with different ratios and SF6 has no obvious difference, and the propagation pattern is also the same. The results of this work can help to better understand the surface discharge phenomenon and the insulation characteristics of C4F7N/CO2 mixture.

Eco-friendly gas insulating medium for next-generation SF6-free equipment

“…The AC flashover voltage of CF 3 I/N 2 is higher than that of SF 6 /N 2 , while it was lower under DC stress. For C 4 F 7 N, the AC surface flashover voltage of 9% C 4 F 7 N/91% CO 2 Eco-friendly gas insulating medium for next-generation SF 6 -free equipment under 0.6 MPa could reach that of SF 6 at 0.5 MPa [115,116] . The negative DC flashover voltage of 4% C 4 F 7 N/96% CO 2 , 8% C 4 F 7 N/92% CO 2 at 0.7 MPa were 96.06% and 101.50% of SF 6 at 0.5 MPa.…”

Insight into charge-induced flashover at the gas–solid interface in DC gas-insulated systems

“…Furthermore, performing dust spraying could itself lead to modifications of the original charge distribution present on insulator surfaces. Recently, some researchers have employed the dust figure technique to help study charge accumulation phenomena [36,37].…”

China's 10-year progress in DC gas-insulated equipment: From basic research to industry perspective

“…It is convenient for dust figure technique to qualitatively obtain surface charge distribution. Chen et al [23,24] employed it to get residual charge distribution after positive and negative surface discharge at the interface between C 4 F 7 N/CO 2 and PMMA subjected to impulse voltages. In their experiments, very fine and detailed patterns of surface charge distribution corresponding to discharge channels were presented by a type of charged dust, i.e., printer toner, as shown in Figures 3(a) and 3(b) .…”