Dielectric strength of alternative insulation gases at high pressure in the inhomogeneous electric field

Sulphur hexafluoride (SF6) is the most common insulation gas in high voltage technology. Besides the excellent insulation properties SF6 has the most known global warming potential with a long lifetime in the atmosphere. Alternative insulation gases have only a fraction of the insulation level of SF6. The electric strength of gases depends on the gas density and can be increased significantly by using higher pressure. The aspirants were Nitrogen, air and N2-SF6-mixtures, with small admixture of SF6. The electron affinity of SF6 increases the dielectric strength of N2 strongly. In general the dielectric strength of SF6 is three times higher compared to air. Therefore the alternative insulation gases must set under high pressure to get equivalent dielectric strength. With regard to the practical feasibility of alternative gases influences like surface roughness, starting electron issue an inhomogeneous electric fields were included in the investigation.