EMP Coupling to Power Lines

A transmission line model of coupling to power lines has been developed that shows the effect of ground conductivity, angle of arrival, polarization, and power line geometry on the open-circuit voltage at the end of the line. With this information, and the characteristic impedance of the line, the current and voltage to any termination may be calculated. This theory has been checked with experimental measurements and shows quite good agreement with measured values of current. The measurements were performed on scale models of power lines. The soil conductivity was scaled appropriately. The results show that, although the transmission-line model is not strictly applicable at the highest frequencies of interest, the error introduced by this approximation is less than the experimental error (¿ ± 10 percent). Measurements have also been made of the propagation of pulses down lines showing effects of attenuation, dispersion, junctions, bends, and spurs. Where available, theoretical calculations have been compared to measured results. From these measurements it is concluded that transmission-line models can adequately be used to predict propagation effects.