Effect of background ions on the selection of the discharge path

The effects of the background ions on the selection of the discharge path i n an air gap have been studied with two different methods. The lightning im pulse air discharge experiment is conducted using an independent ion genera tor, while the air discharge experiment uses a lightning impulse superimpos ed on a. de high voltage used to produce background ions. The influence of different background ions on the leader development, and thus on the discha rge path, is observed. Consistent results have been obtained with the two m ethods. The probability for the discharge path passing through the negative ion space is much higher than that for the passing through the positive io n space. The mechanism of the effects of background ions is analysed based on the electron avalanche and the electric field.