Computation of Lightning-Induced Voltages for Striking Oblique Cone-Shaped Mountain by 3-D FDTD Method

This paper analyzes the effect of lightning strikes to an oblique cone-shaped mountain on the lightning-induced voltages on the power distribution line. The lightning-generated electromagnetic fields are calculated by using a three-dimensional finite-difference time-domain method in Cartesian coordinates, and the lightning-induced voltages are computed by means of Agrawal coupling model. The simulation results are presented for an oblique cone-shaped mountain with different inclining angles, and for different relative positions of the distribution line placed over nonflat lossy terrain. It is found that, when lightning strikes the top of an oblique cone-shaped mountain, the lightning-induced voltages are closely related with the mountain inclining angles where the distribution line is located above as well as the other mountain inclining angles; in general, the peak values of induced voltages increase with increasing inclining angles. For example, for the constant angle β = 45° (the inclining angle where the line is located above), the induced voltages at the close end of line for α = 26.6°, 45°, and 63.4° (the inclining angle opposite to angle β) is increased by 24%, 60%, and 106% as compared with that for flat ground, respectively.