Accuracy of the Inverse Fast Fourier Transform algorithm in grounding grid transient analysis

In this paper, accuracy of the Inverse Fast Fourier Transform (IFFT) algorithm is analysed, when used to compute the potential distribution in grounding grid transient analysis. The accuracy of the classical IFFT algorithm is questionable when the computations are carried out at relatively large distances between field points and source points. Accuracy deficiencies of the classical IFFT algorithm and the modified IFFT algorithm used in the well-known program package CDEGS are analyzed. Accuracy of these algorithms is tested using a highly accurate algorithm for computing the inverse Fourier transform based on numerical integration. Computation of the scalar potential distribution due to a point current source in unbounded and uniform earth is used as an illustrative test example.