Dielectric strength of alternative insulation gases at high pressure

Summary

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. 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. Therefore the investigation of alternative insulation gases especially breakdown measurements were executed up to pressures of 2.6 MPa. The aspirants were air, O2, N2, O2-N2-mixtures, CO2 in comparison to SF6 and SF6-N2-mixtures. With these measurements the electrical breakdown strength of alternative insulation gases in quasi-homogeneous and also the slightly inhomogeneous electric fields and the applicability of the Paschen-parameters at high pressure have been investigated. With regard to the practical feasibility of alternative gases influences like surface roughness, starting electron issue and strong inhomogeneous electric fields were included in the investigation. To get a closer view to the beginning of high pressure breakdown behaviour, measurements of the pre-discharge current in slightly and strong inhomogeneous electric field arrangements also were carried out. The pre-discharge current was measured at DC-voltage stress and it dependency to homogeneous factor, surface roughness and pressure. The electric field strength was varied in the range from 3 MV/m to 60 MV/m and the maximum voltage was 320 kV DC and up to 700 kV BIL.

Additional informations

Authors

Wang Can, Schober Fabian, Küchler Andreas, Liebschner Marcus