Browsing by Author "Clemence, Respicius"

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    Lightning protection of medium voltages and low voltages electrical power networks
    (University of Dar es Salaam, 2007) Clemence, Respicius
    In order to achieve better lightning protection and Electromagnetic Compatibility (EMC) requirements for the electrical power networks, it is important that the knowledge of surge propagation on the power lines should be well known to protection engineers. This includes the knowledge of identifying the points on power lines which would have the probability of having the higher values of induced surge voltages for a particular Electrical Power Network in the event of a lightning strike terminating on the line or close to the line. Therefore, this work investigates the various factors that could influence the induction and propagation of transient surges in an Electrical Power Network when direct lightning strikes terminate on one of the overhead conductors that has a greater probability of being struck. In this work, the Medium Voltages and Low Voltages (MV/LV) Electrical Power Network (overhead primary and secondary distribution lines) have been modelled as Multi Transmission Lines system (MTLs) for transient propagation studies. Two cases of transmission line parameters representation have been considered i.e. lossless and lossy (conductor internal loss) conductors. The simulation results of lossy consideration differ slightly from the simulation results of lossless cases in terms of wave shapes and peak magnitudes of the induced voltage. In this study the struck conductor of the overhead primary and secondary distribution lines is referred as the emitter whereas other conductors below the emitter are referred as receptors. With different loads at the ends of the receptors, it has been found that the peak surge voltage is the highest on the emitter near the point of strike when all receptors are terminated with very low impedances. On the other hand, the obtained peak induced voltage is higher at either ends of each receptor when the receptors are terminated with very high impedance.