A one-dimensional thermo-hydrodynamic model for upward leader inception considering gas dynamics and heat conduction

•A 1D-THD model is proposed to calculate upward leader inception.•A Mach–Zehnder interferometer was set up to observe leader discharges.•Experimental and calculation results of leader channel expansion show agreements.

Modeling of upward leader inception is important for lightning risk assessment of high voltage transmission systems. The classical thermodynamic model for long gap leader discharge proposed by Gallimberti has been widely adopted for about 30 years and applied to the analysis of unstable upward leader inception, taking gas temperature rising to 1500 K as the criterion. However, the gas dynamic process and heat conduction which have influences on the gas temperature and leader diameter are not fully considered in this model. Theoretical analysis and simplified simulation illustrated that there are a few limitations without taking the two factors into account. In this paper, the gas dynamics and heat conduction have been considered, and a modified one-dimensional thermo-hydrodynamic (1D-THD) model has been proposed to calculate the inception of upward leader. This model also applies to leader channel expansion. Besides, a Mach–Zehnder interferometer was set up to observe the gas density variation and radial expansion of heated leader channels. The calculation results of the channel expansion have good agreements with experimental data.