A transient model of lightning breakdown process based on photographic measurements

In this paper, the positive pre-discharge under lightning voltage impulses has been analyzed. The standard lightning voltages up to u̅ = 2.4 MV have been applied to the air gaps up to s = 4 m. The pre-discharge current of rod-electrode in mA-range has been measured. Additionally, during the very short time that the pre-discharges are growing in the atmospheric air (μs-rang), some high speed photos have been recorded from the instantaneous structure of pre-discharge by a high speed camera. Based on the taken photos, the electric charge distribution has been calculated. As the main goal, the charge simulation method has been modified to calculate the electric field with the existence of the spatial electric charge, which has been produced by the ionization and deionization (recombination) activities during the development of pre-discharge in the atmospheric air. The variation of the electric field during the pre-discharge (e.g. during a period of about 200 ns) has been calculated. The simulations demonstrate plausible results and verify the dependency of the pre-discharge development velocity in the air on the electric field.