Preliminary Study on Spatio-Temporal Currents in the Strokes with Long Upward Leaders

Long upward connecting leaders are seen from tall objects on ground. The bridging between the downward and upward leaders through their streamer zones, initiates the return stroke. Two current waves, one heading towards the ground and the other moving upward are initiated. The downward moving wave reaches ground through the object and then gets reflected (back removed). The velocity of propagation of the downward wave is expected to be different in the channel and the tall object (or down conductor). The upward wave then catches up with the wavefront and the literature is divided on its fate. In any case, the spatio-temporal distribution of the current, at least below the bridging zone, can be expected to be different from that with strike to ground. This finds interest not only from the phenomena perspective, but also from the protectional aspects. In this preliminary work, an investigation on the spatio-temporal current evolution is carried out for strokes with significant upward leaders arising from a 100 m tall slender tower (down conductor). It will be compared with the strike to ground case for the same leader configuration.