Numerical approximation of the lightning current function

In this paper the lightning current function proposed in IEC 62305-1 is approximated by a linear combination of exponential functions in the time domain, which will afterwards be analytically transformed into the frequency domain. The unknown coefficients of the exponential approximation are computed using the least squares method. Lightning current function in the frequency domain can be used for transient analysis of electromagnetic phenomena that include lightning protection, grounding grid analysis and electromagnetic compatibility problems.