Modification of streamer-to-leader transition model based on radial thermal expansion in the sphere-plane gap discharge at high altitude

Abstract Historically, the streamer-to-leader transition studies mainly focused on the rod-plane gap and low altitude analysis, with limited attention paid to the sphere-plane gap at high altitude analysis. In this paper, the sphere-plane gap discharge tests were carried out under the gap distance of 5m at the Qinghai Ultra High Voltage (UHV) test base at an altitude of 2200m. The experiments measured the physical parameters such as discharge current, electric field intensity and instantaneous optical power. The duration of the dark period and the critical charge of streamer-to-leader transition were obtained at high altitude. Based on radial thermal expansion of streamer stem, we established a modified streamer-to-leader transition model of the sphere-plane gap discharge at high altitude, and calculated the stem temperature, stem radii and the duration of streamer-to-leader transition. Compared with measured duration of sphere-plane electrode discharge at an altitude of 2200m, the error rate of the modified model was 0.94%, while the classical model was 6.97%, demonstrating the effectiveness of the modified model. From the comparisons and analysis, several suggestions are proposed to improve the numerical model for further quantitative investigations of the leader inception.