Influence of Water Film Over Sphere- Sphere Electrodes on Power Frequency Discharge Characteristics of Air Gap

The water film on the surface of the electrode affects the breakdown voltage of the air gap, but the mechanism of the influence is not clear. Herein, the sphere-sphere air gap is taken as the investigated research models. The breakdown voltage of the both electrodes coated with water film is higher than the dry electrodes at the sphere-sphere air gap. However, when the gap distance increases from 1cm to 6cm, the amplification of breakdown voltage decreases from 27.2% to 4.44%. The increase of breakdown voltage is because that the streamer is negative in the sphere-sphere gap, the starting photoelectrons of the secondary electron collapse originate from the photoionization of the cathode, the water film leads to the increase of energy of initial photoelectron, and the decrease of amplification of breakdown voltage is caused by the field distortional and increasing of gap distance.