Zhuang Chijie

Experimental Study on Branch and Diffuse Type of Streamers in Leader Restrike of Long Air Gap Discharge

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.

Research on shielding failure of UHVDC based on leader progression model

Shielding failure is one of key problems of UHV transmission lines. Considering the high operating voltage and high tower of UHV transmission lines, the inception criterion of upward leader is proposed in this paper. The process of shielding failure is simulated by the method based on leader progression model and shielding failure rate is calculated. This method is verified by comparing the calculation results with the operated data of UHV transmission lines in Japan. The shielding failure characteristics of UHVDC transmission lines in China under different terrain conditions are researched.