AC Volume Breakdown and Surface Flashover of a 4% Novec^TM 4710/96% CO₂ Gas Mixture Compared to CO₂ in Highly Nonhomogeneous Fields

• Main Authors: Houssem Eddine Nechmi, Mohammed El Amine Slama, Abderrahmane (Manu) Haddad, Gordon Wilson
• Format: Article
• Language: English
• Published: MDPI AG 2020-04-01
• Series: Energies
• Subjects: Novec^TM 4710/CO₂; CO₂; surface discharge; volume discharge; glow corona; surface roughness
• Online Access: https://www.mdpi.com/1996-1073/13/7/1710

AC pre-discharge currents, breakdown, and flashover voltage measurements are reported in a 10 mm needle-plane arrangement in a 4% Novec^TM 4710/96% CO₂ gas mixture and compared with CO₂ for pressures up to 8.8 bar abs. Flashover measurements were performed on different solid dielectrics (Al₂O₃_filled epoxy resins, PTFE (Polytetrafluoroethylene) and PE (polyethylene)) for different roughness surface finishes. The effect of fixed conducting needles at various positions on electrical strength is reported. A strong nonlinear behaviour as function of gas pressure was observed for all the studied parameters (gas, needle position, solid insulator, insulator roughness). The non-linear behaviour is attributed to the inception and quenching of glow corona, in the interval between inception and breakdown or flashover voltages. It is found that a 4% concentration of Novec^TM 4710 in CO₂ has a breakdown/flashover voltage ≈ 1.14 higher than CO₂. The glow corona-induced stabilization effect is seen for pressures between 2 and 5 bar abs for all the studied parameters. The peak flashover voltage and its associated pressure of the different insulators are strongly dependent on surface roughness. At 8.8 bar abs, the flashover voltage level obtained with various materials was ordered as follows: PTFE > PE-UHMW > Epoxy > HDPE(High-density polyethylene).