中文摘要：

One of the main problems in the Ultra High Voltage(UHV) transmission project is to choose the external insulation distance,which requires a deep understanding of the long air gap discharge mechanism.The leader-streamer propagation is one of most important stages in long air gap discharge.In the conductor-tower lattice configuration,we have measured the voltage,the current on the high voltage side and the electric field in the gap.While the streamer in the leader-streamer system presented a conical or hyperboloid diffuse shape,the clear branch structure streamer in front of the leader was firstly observed by a high speed camera in the experiment.Besides,it is found that the leader velocity,width and injected charge for the branch type streamer are greater than those of a diffuse type.We propose that the phenomenon results from the high humidity,which was 15.5-16.5 g/m~3 in our experiment.

英文摘要：

One of the main problems in the Ultra High Voltage （UHV） transmission project is to choose the external insulation distance, which requires a deep understanding of the long air gap discharge mechanism. The leader-streamer propagation is one of most important stages in long air gap discharge. In the conductor-tower lattice configuration, we have measured the voltage, the current on the high voltage side and the electric field in the gap. While the streamer in the leader-streamer system presented a conical or hyperboloid diffuse shape, the clear branch structure streamer in front of the leader was firstly observed by a high speed camera in： the experiment. Besides, it is found that the leader velocity, width and injected charge for the branch type streamer are greater than those of a diffuse type. We propose that the phenomenon results from the high humidity, which was 15.5-16.5 g/m3 in our experiment.