|Title:||Modelling of semi-random growth of trees during the electrical breakdown of solid insulation|
Hong Kong Polytechnic University -- Dissertations
Department of Electrical Engineering
|Pages:||vi, 102,  leaves : ill. ; 31 cm|
|Abstract:||Four computer models have been developed in this dissertation to simulate electrical trees. The first model considers only spacial probability. The second model assigns the probability of discharge of a branch proportional to its estimated electrical stress. Stress angle, discharge score and minimum score are introduced in the second model in order to simulate bush and branch trees. The third model includes a discharge time for each discharge step and can therefore simulate the overall tree growth rate. Integrating the algorithms of the first three models, the fourth model simulates trees in three dimensions. Apart from giving different 3D perspective views, the model produces data comparable with findings of researchers. Investigation results of other researchers such as varying resistivity of tree branches, build up of gas pressure inside tree branches, deposition of space charges, limitation of electron avalanche build up inside narrow channels had been considered when developing the models. In addition, the third and the fourth models adopted the assumptions widely assumed by researchers: (a) there is a critical stress below which the discharge activities would cause negligible damage to the dielectric material and (b) the time to form a new branch is proportional to the difference between the local electrical stress and the critical stress.|
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