Prebreakdown Phenomena in Insulating Gas Mixtures under Very Fast Transients

For further improvement of the insulation for high voltage gas insulated transmission lines an alternative gaseous medium is needed in order to substitute completely or at least partially the expensive gas SF₆. This aspect is also important with respect to environmental considerations (greenhouse effect). As a possible alternative to pure SF₆ or SF₆/N₂ (10% / 90%) gas mixture, SF₆/CO₂ (10% / 90%) gas mixture was chosen (Pfeiffer, 2006). Prebreakdown phenomena under very fast transient voltage stress in the gas mixture were investigated for inhomogeneous field distribution. The following parameters were considered: Pressure range from 0.1 to 0.8 MPa, electric field utilisation factor of the electrode configuration 2.5%, peak voltage applied up to 160 kV. Both electrical and optical investigation methods were used in the present work.