Inverse Fourier transform for transient calculations

A method is presented for the calculation of the energisation transients in overhead transmission lines. The method is capable of handling lumped and distributed parameters and of taking into account their frequency variation. The method is based on calculating the frequency spectrum of the transient under investigation, and then inverting to the time domain. The poles of the spectrum laying on the imaginary axis are isolated before inversion is carried out. The steady state part of the time response is calculated separately and added. Numerical inversion problems are studied and rules for carrying out this process are given. The method is tested for the case of single conductor lines and results are presented. The effect of varying the line length or ground resistivity on the energisation transient is discussed. In a separate paper the extension of the method to the case of a general N conductor transmission line is presented with the relevant results. The method presented provides an accurate but not a cumbersome means for calculating energisation transients.