Lightning strikes to buildings and earthing techniques

When lightning strikes an air terminal of a lightning safety system on prime of a constructing the high-frequency currents movement downwards alongside the interconnected conductors.

The currents which movement alongside the conductors are known as longitudinal currents and these exist in each the above- and under floor conductors. As present flows alongside the conductors within the community a voltage rise happens which is most on the air terminal location and is attenuated alongside the conductors since like every electrical conductor, the conductors exhibit impedance to the movement {of electrical} present. As soon as the currents attain the buried earthing they’re leaked into the bottom, known as leakage currents, which is dependent upon the sequence and mutual impedances between the conductors within the soil.

The high-frequency currents as they’re dissipated create a possible rise within the surrounding soil leading to floor voltages, in addition to contact or step voltages hazards.