Plasma-Chemical Decomposition of Gas Mixtures Applied for Electrical Insulation

Th. Hammer and T. Kishimoto

Siemens AG, CT RTC PET, Erlangen, Germany

Abstract- In MV and HV energy distribution facilities gas mixtures containing SF6 are successfully applied for dielectric insulation. Their dielectric strength staying stable over more than 30 years guarantees reliable operation for the complete lifetime of the facility. Because of the global warming potential of SF6 recently gas insulation with alternative gas mixtures was investigated. We performed experiments simulating the long term exposition of a gas mixture containing 40% N2O in N2 to partial discharges. Gas samples filled into a closed vessel were exposed to dielectric barrier discharges. During these tests the electrical properties of the dielectric barrier discharge reactor were monitored. At the end of each test the treated gas sample was analyzed by means of Fourier transform infrared absorption spectroscopy. Applying a specific input energy density of 180 J/lSTP resulted in formation of NO and NO2 with concentrations as high as 586 ppmvol and 156 ppmvol, respectively. The dielectric strength of the gas mixture did not degrade.

Keywords- Dielectric insulation, gas mixture, partial discharge, plasma-chemical degradation

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