Shielding Effect of Surrounding Buildings on the Lightning-Generated Vertical Electric Field at the Top of a Tall Building

We have evaluated the vertical electric field E-z on the roof of a 100-m tall building considering the shielding effect of surrounding buildings (the shields) due to nearby lightning return strokes to flat ground by using the 3-D finite-difference time-domain method. Also, we have investigated the influences on the vertical electric field E-z and corresponding enhancement factors of the following parameters: the distance d between the strike point and the field point; the length l of plan area, the height h, and the conductivity is of the shields; and the relative position and relative distance rd between the field point and those shields in its vicinity. In general, vertical electric fields and enhancement factors at the field point can be reduced because of the effect of the shields in its vicinity. The effect for the shield located in front of the field point is much stronger than that for the shield located in any other positions. Moreover, the dependence of shielding effect on height h of the shield is stronger than any other parameters such as distance d, relative distance rd, and length l of the shield.