Experimental Study and 3-D Modeling of Positive Streamer Discharges Under the Effect of Humidity

The research on streamer discharges not only provides support for insulation design of high-voltage power transmission systems, but also lays a theoretical foundation for lightning discharges. The macroscopic parameters of streamer discharges have been investigated, but there is a lack of analysis on the development and branching characteristics of streamers under the effect of humidity. In addition, different types of models have been built to simulate streamer propagation. However, there are few 3-D models which simulate branching process of multiple streamers at different humidity. In this work, a discharge experimental platform with controllable environmental parameters has been built. The effect of the humidity of 4.5-19.1 g/m(3) on streamer propagation and branching has been experimentally studied. Then, the 3-D "discharge tree" model of collective streamers is improved, in which the streamer branching incorporates the photoionization in humid air. Furthermore, we compare the results of the 3-D simulation model with the experimental data. Through the simulation model, the streamer parameters such as line charge density and electric field distribution are obtained. The results show that the electric field of streamer channels is larger when the humidity is higher, but the propagation velocities are reduced. The humidity has limited the effect on the streamer branching ratio.