Empirical Formula of Effective Coupling Length for Transmission Lines Illuminated by E1 HEMP

This paper presents empirical formulas of the effective coupling length (ECL) for the transmission lines illuminated by the horizontally or vertically polarized E1 HEMP, which is defined by the IEC standard. Based on the analysis and the numerical data of the ECL, the empirical formulas are developed through fitting first. Then, the empirical formulas are inspected and the results show that the empirical formulas can cover the range of the numerical values of the ECL well. At last, the empirical formulas are adopted to simplify the analysis of the HEMP coupling with a transmission line network. The results show that the ECL can greatly simplify the computation of the HEMP coupling with large transmission line networks but is not suitable for the line which the E1 HEMP coupling with is weak.