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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.

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When faced with a new design problem, Engineers most often tend to rely on their accumulated knowledge of science, mathematics, and appropriate experience to reach suitable solutions. Case-Based Reasoning is a new engineering paradigm that reflects this fact by suggesting solutions to novel problems based on the recall and reuse of specific experiences. Such a paradigm relies on previous successful design solutions that are stored in the form of separate cases in a database. / The aim of this thesis is to develop a process that will provide examples which can be used to set up a database of optimized designs for various electromagnetic devices such as loudspeakers and actuators. Each stored design will represent an optimum solution to a specific set of requirements for an electromagnetic device. These designs will eventually be used by a case-based reasoning system to reach a solution for possible requested future designs. The process will also involve developing a parameterization of a particular class of devices as well as testing optimization processes to be applied to the initial designs in order to ensure that the solutions stored in the case database represent effective and realistic devices which satisfy the requirements. This thesis also presents test results that illustrate how each optimized design conforms to certain requirements set as an input objective.