Transient formulation of lossy ground return parameters for time-domain transmission line analysis

New expressions of the ground impedance and admittance matrices for multiconductor line simulation are proposed, which are valid in a wide frequency-range. The time-domain formulation of the ground return parameters is obtained analytically by the inverse Fourier transform, based on the rational approximation in the frequency-domain. In the time-domain telegraphers' equations the convolution terms including the transient ground parameters are rearranged in order to achieve a more efficient implementation in numerical solution codes. The sensitivity of the proposed model to the ground conductivity and line geometrical parameters is investigated with reference to a three-conductor line. Comparisons with the results obtained by using the Carson ground impedances are carried out.