Development of a Fast and Efficient Macromodel for Nonuniform Electromagnetic Field Excitation of Transmission Lines
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In this thesis, the problem of overvoltage calculation on multiconductor transmission lines due to nonuniform external electromagnetic field excitations, such as lightning, is investigated by introducing a field-voltage macromodel. The main purpose of this thesis is to find a fast and efficient algorithm to model the effect of the radiated electromagnetic fields on transmission lines. This is done by replacing distributed voltage and current sources along the transmission line which are as a result of external electromagnetic field radiation, by voltage and current sources at the terminals of the transmission line. For this purpose, the knowledge of electromagnetic field at every point on the transmission line is required. A transfer function based pole-residue tracing technique will be introduced in this thesis. By using the proposed algorithm, a closed form solution for the lumped sources at the terminals of transmission line in the frequency domain is obtainable. This approach will enable us to bridge the software working in frequency domain with those working in the time domain. The effect of different parameters on calculated overvoltage such as finite conductivity of the ground and lightning return stroke channel (RSC) specifications are studied. The theoretical background and extent of validity of the proposed algorithm are reviewed in this thesis.