Simulation Study on the Influence of Initial Electron Concentration on Streamer Discharge in SF₆ Needle-plate Gap

The positive streamer discharge model of SF<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</inf> gas in 1 mm needle-plate gap was constructed. By simulating the streamer propagation process under different initial electron concentration N<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e0</inf> (10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">9</sup>-10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15</sup> m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup>) the influence of this parameter on the dynamic characteristics of streamer discharge is revealed. The simulation results show that for every 2 orders of magnitude increase in N<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e0</inf>, the development rate increases by 28% on average, and the breakdown delay is shortened synchronously. With the increase of N<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e0</inf>, the peak field intensity of the streamer head gradually decreases, and the peak area migrates to the cathode side. The electron density distribution shows bipolar agglomeration characteristics. With the increase of N<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e0</inf>, the peak value of electron density near the tip increases sharply, while the peak value near the streamer head decreases slightly. The streamer channel radius is less affected by the initial electron concentration.