A transmission-line-type model for lightning return strokes with branches

• We examine the effect of channel branching on electric field waveforms produced by first return strokes in negative cloud-to-ground lightning using a modified transmission line model.
• Presence of an ungrounded branch results in sharper initial peak and a secondary peak in the falling part of the return stroke waveform.
• The effects of the height of the branching point above ground, fraction of total channel current flowing to the branch, and current reflections from the branch unconnected end are illustrated.

We examine the effect of channel branching on electric field waveforms produced by first return strokes in negative cloud-to-ground lightning using a modified transmission line model. From computed return stroke electric field waveforms it is found that the presence of an ungrounded branch results in sharper initial peak and a secondary peak in the falling part of the return stroke waveform. The time interval between the primary and secondary peaks depends upon the height of the branching point above ground and the speed at which the incident current wave moves upward from the ground. The presence of branch serves to slightly decrease the magnitude of the opposite polarity overshoot. The effects of the height of the branching point above ground, fraction of total channel current flowing to the branch, and current reflections from the branch unconnected end are illustrated.