A new formulation for lightning return-stroke models of engineering type

A new formulation for lumped-source-type (transmission-line-type) lightning return-stroke models is proposed. This formulation expresses the longitudinal current at height z’ as the channel-base current minus the overall longitudinal current change from ground surface to z’. In general, the longitudinal current change consists of two components, one of which is associated with the upward propagation delay (transferred charge density component) and the other with the radial corona current (deposited charge density component). For the original transmission line (TL) model, there is no radial corona and, hence, no longitudinal current change due to corona current. For infinitely large current-wave propagation speed (as assumed in the Bruce-Golde model), there is no propagation delay and, therefore, in this case the longitudinal current change due upward propagation delay vanishes. The new formulation allows one to gain new insights into the lightning return stroke process.