Evaluation of space-charge behaviour in long airgap using Pockels´ cells

The behaviour of space charge produced by the first corona in a long rod-plane gap under a negative switching impulse voltage was analysed based on the measurements of electric field using Pockels´ effect. After examining the reproducibility of the discharge phenomena, the radial and axial electric-field intensities in the gap were measured. The electric-field distribution was obtained based on the measurement at 39 positions in the gap during a series of voltage applications. The space-charge field was analysed assuming an axial symmetry of the phenomena, and the spatial expansion of the charge was discussed.