Validating the Phase-to-Phase Gap Distance of Unconventional High Surge Impedance Loading Transmission Line Using Propagation Viability of Arc by Numerical Analysis

Determining appropriate phase-to-phase gap distances is critical to withstand phase-to-phase switching overvoltages in unconventional high surge impedance loading (HSIL) transmission lines. This paper presents a numerical approach to validate gap distances by analyzing the propagation viability of leaders and streamers under switching impulses. The study integrates Rizk's semi-empirical model and Gallimberti's time-domain leader-streamer theory to establish a robust theoretical foundation for air breakdown within the minimum distance of the closest phase. Using COMSOL Multiphysics, the electric field distribution across the phase gap was calculated to identify regions of maximum and minimum field intensities. Propagation viability curves were generated to evaluate the conditions under which the leader-streamer system could sustain propagation through the region of the minimum electric field. The calculated minimum breakdown voltage was validated against numerical simulations, ensuring its reliability for unconventional transmission line configurations.