Masters Dissertations

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Browsing Masters Dissertations by Author "Damas, Jacqueline"

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    Some factors that might influence the lightning protection aspects in a telephone link between exchange and subscribers
    (University of Dar es Salaam, 2008) Damas, Jacqueline
    The studies presented in this thesis contribute to the understanding of lightning induced transient over voltages and their protections on the telephone lines networks in Tanzania. Induced overvoltage’s and currents on overhead telephone lines due to lightning-induced transient electromagnetic excitation and the efficiency of Metal Oxide Varistors (MOV) for protection of overhead telephone line against transient surge were modelled in this thesis. Induced over voltages and currents in the telephone line were calculated on a conductor of 7m height above the ground and /m depth below ground. Using Finite Difference Time Domain (FDTD) method induced overvoltage was calculated as a function of distance from the strike point using MATLAB 7.0 package. Simulated results showed that induced overvoltages by direct strike were more severe compared to indirect strike and were associated with ground property. Three different ground conductivities; O. /mS/m, /mS/m and 10mS/m showed that the poorer the ground conductivity, the higher the induced voltage on the line at the strike point. However, variation of height of telephone line by /m from the 7m i.e. 6m, 7m and 8m showed no significant difference in the induced peak voltages even when the effect of ground conductivity was considered. In addition, the suitability of MOV for the protection of the telephone line termination points was also studied in this work. Induced lightning overvoltage’s on a telephone line based on different models for a fast transient lightning surge of peak value 10kA (0.11/200) using ATP-EMTP package showed that the Pinceti et al model replicates much closely the peak voltages specified by manufacturer's data for both fast and slow lightning transient surges compared to Non-linear resistor-model.