3-D FDTD Computation of Lightning-Induced Voltages on an Overhead Two-Wire Distribution Line

Lightning-induced voltages on a 738-m long overhead two-wire line have been computed using the 3-D finite-difference time-domain (3-D FDTD) method for solving Maxwell's equations. The 3-D FDTD method employed here uses a subgrid model, in which spatial discretization is fine (cell side length is 0.9 m) in the vicinity of overhead wires and coarse (cell side length is 4.5 m) in the rest of the computational domain. The overhead wires having radii of some millimeters are simulated by placing a wire having an equivalent radius of about 0.2 m (approximate to 0.23 x 0.9 m) in the center of an artificial rectangular prism having a cross-sectional area of (2 x 0.9 m) x (2 x 0.9 m) and the modified (relative to air) constitutive parameters: lower electric permittivity and higher magnetic permeability. Induced-voltage peaks computed at different points along the line for the return-stroke speed of 130 m/mu s and ground conductivity of 3.5 mS/m agree reasonably well with the corresponding voltage peaks measured in the rocket-triggered lightning experiment of Baker et al., in 1996.