Investigations on voltages and currents in lightning protection schemes involving single tower

A reliable protection against natural lightning has become very essential for modern critical systems. For very vulnerable systems, the protection system is physically isolated from them. In such cases, towers taller than system being protected are generally employed. The maximum allowable bypass current and the so-called rise in potential during the strike decide the height and location of such towers. For tall towers, TM modes dominate at least during the rising portion of the current making the analysis very complicated. In view of this, for a better assessment of the potential at the top and the base currents, experimental investigation in the frequency domain is carried out on the electromagnetically scaled model of the actual tower. The possible reduction in the tower base currents with the connection of ground wires and the influence of neighboring structures on the tower surge response are also studied. Investigations are also carried out on an alternative design involving mast insulated from the supporting tower and a separate set of ground wires acting as down conductors. Some analysis on the electric withstand capabilities of the insulating support is also made. The findings of the present work are believed to be quite useful to lightning protection engineering.