Coupling between over-head transmission lines and lightning electromagnetic fields

Abstract

In terms of the generation of the over-voltage, caused by the coupling between overhead transmission lines and lightning electromagnetic fields, an experimental model was built to simulate the coupling, based on the theoretical analyses. It is concluded that when the overhead transmission lines couple with the lightning electromagnetic fields, there is less low frequency component but more high frequency one in its spectrum than the source, thus the coupled waveform is steeper, and the time is shorter than the excitation waveform, about 2 $\mu$ s; Meanwhile, the coupled voltage linearly increases with the addition of the electric resistance while the resistance of overhead transmission lines is below 510 $\mathrm{\Omega }$ , however, if the resistance is above 300 k $\mathrm{\Omega }$ , the circuit approximates an open one; The peak value of the coupled voltage has a positive correlation with the increase of the height and the length, while the height ranging in 1–3 m and the length in 10–30 m. There is an accordance between the experiments and the theoretical analyses, which is significant to the lightning protection on transmission lines.