Modeling and Calculation for Conductive Coupling Caused by Lightning Over-Voltage in Substation Based on Numerical Inverse Laplace Transform

A method in allusion to the arbitrary waveforms source for using Numerical Inverse Laplace Transform (NILT) is proposed in this study. The principle of this method is to consider the arbitrary waveforms source containing of M data points as M-1 discontinuous functions. By means of the unit step function, the M-1 discontinuous functions can be expressed as a unified form, and then the frequency domain expression of the arbitrary waveforms source can be get using the basic properties of the Laplace Transform, which could conquer the limitations to the source in application to NILT. The experiments circuit for simulating conductive coupling caused by lightning overvoltage through potential transformer is put up in the laboratory and the cascade two-port transmission parameters model is built based on the frequency domain measurements by means of vector fitting. The coupling voltage at the terminal of the second cable is simulated by NILT. The comparison between the calculated results and measured data verify the feasibility of this method.