Direct lightning strike to a building

Because direct lightning strikes relatively few buildings, there is a tendency to underestimate the risk of direct lightning strikes. However, because the threat of lightning strikes to high-rise buildings is very high, it should be assumed that lightning strikes occur in these buildings. Under these assumptions, we need to consider how much damage the LAN inside the building will have.

When there is a direct lightning strike, the lightning current flows through the building's lightning protection system. Figure 3 shows how Side-Flash occurs. Lightning strikes a lightning rod and flows downward through a lightning wire in the wall of a building. When a rapidly changing current flows through a conductor, a voltage is induced in the cable due to the cable's inductance. According to the figure, 1.5 MV is induced in a 30 m conductor. At this time, a slightly weaker case such as ground potential can be a voltage induced by capacitive or inductive coupling (Figure 4). The voltage induced by capacitive coupling attenuates rapidly as the cable passes through a grounded metal duct.