Research on the characteristics of upward leader emerging from the transmission lines influenced by operation voltage

The problem whether the DC operation voltage can influence the characteristics of upward leader emerging from transmission lines is still in question since experiments and observation data is insufficient. It is necessary to study the relationship between the characteristics of the upward leaders and operation voltage. This paper presents some simulated experimental results of a combined plane-rod (PR) electrode to conductor air gap of 7 meter length. A current measuring instrument with frequency response of from DC to 6.5MHz was developed and used to measure the leader current. Besides, high speed CCD camera was used to observe the optical phenomenon of the whole process. The 200/2000μs impulse voltage up to 4MV and positive DC voltage up to 800kV was applied to the electrode and conductor respectively. The higher charge per unit in the leader channel and earlier inception time has been found along the higher DC voltage. These results have been compared with those in the gap that only impulse voltage was applied. Finally, the influence of positive DC voltage on the characteristics of upward leaders was discussed.