AC Breakdown Characteristics of C₅F₁₀O/CO₂ Gas Under Different Electrode Surface Roughness

In this work, we explored the ac breakdown characteristics of C₅F₁₀O/CO₂ mixtures under different electrode surface roughness. It was found that sulphur hexafluoride (SF₆) outperforms C₅F₁₀O/CO₂ mixtures in the ac breakdown experiments. The breakdown voltages of C₅F₁₀O/CO₂ and SF₆ are negatively correlated with the surface roughness, while SF₆ is more sensitive to the electrode surface roughness than C₅F₁₀O/CO₂. To reach the dielectric strength of SF₆, an increase in pressure or mixing ratio of C₅F₁₀O/CO₂ is needed, while the liquefaction temperature of C₅F₁₀O/CO₂ will increase simultaneously. Considering the limitation of 20% drop in dielectric strength, the maximum acceptable surface roughness of the gases is determined. The controlling requirement of electrode surface roughness ${R}_{t}$ of 30 $\mu \text{m}$ in SF₆ equipment is suitable for the design of C₅F₁₀O/CO₂ equipment.

I. Introduction

Sulphur hexafluoride (SF₆) has been widely used in gas insulation equipment due to its excellent dielectric strength and arc quenching properties [1]–[4]. However, SF₆ is a strong greenhouse gas with a global warming potential (GWP) value up to 23 500 (100 years’ time horizon) and the atmospheric lifetime of approximately 3200 years [5], [6].