Dynamic Balancing between Thermal -Field Emission Currents of Series-connected Vacuum Gaps

• Published in: 2023 30th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV) pp. 721 - 724
• Main Authors: Ding, Jiangang, Mu, Shengquan, Yao, Xiaofei, Liu, Zhiyuan, Wang, Jianhua, Geng, Yingsan
• Format: Conference Proceeding
• Language: English
• Published: IEEJ 25.06.2023
• Subjects: Breakdown voltage; Couplings; Electric breakdown; Insulation; Lighting; series-connected vacuum gaps; Space charge; thermal-field emission; Vacuum breakdown
• ISSN: 2471-786X
• DOI: 10.23919/ISDEIV55268.2023.10200790

The objective of this paper is to study thermal- field emission during prebreakdown process of series-connected vacuum gaps. Thermal-field emission of a microtip on cathode surface of on single vacuum gap was calculated via the MurphyGood theory considering the Nottingham effect, space charge and nano-scale curvature radius. Then through the bidirectional coupling of the aforementioned model and circuit model, thermal-field emission current of series-connected vacuum gaps was calculated. Results showed that a selfbalancing process that emission currents of series-connected vacuum gaps tend to be consistent existed during the prebreakdown process. This explains the astonishing synchronicity on breakdown instant of the series-connected vacuum gaps that was sometimes observed. However, time to reach a balanced emission current could be prolonged by adopting grading capacitors in parallel with the vacuum gaps. This explains the high probability of asynchronous breakdowns observed for series-connected vacuum gaps under lighting impulse voltage.