performance of high voltage outdoor insulators can be greatly affected by weather conditions. The weather conditions under investigation are cold temperatures coupled with high humidity levels. Weather data from a number of coastal stations around South Africa was analyzed to determine whether surface condensation was likely on outdoor insulators under these weather conditions. A heat transfer equation was used to determine the response of the insulator surface temperature to the environmental temperature. It was found that surface condensation would occur on the insulator surfaces which would lead to sudden, heavy wetting of the surface. Outdoor insulators in coastal environments are often heavily polluted, due to salt spray, and when wet, a conductive layer can form on the insulator surface. This conductive layer can result in appreciable leakage currents flowing on the insulator surface, often leading to premature failure. The finite element method program, Maxwcll, was used to simulate the outdoor insulators both under these polluted, wet conditions and under unpolluted conditions. Both cases were simulated for a silicone rubber, glass cap-and-pin and two EPDM outdoor insulators. The polluted insulators were simulated with varying pollution severities. The results of the simulations are analyzed and the surface resistances of the wet polluted insulators were calculated. An experiment was' set up to mask the environmental weather conditions found which would lead to surface condensation. The insulators under test were placed in a chilled weather chamber which introduced a steam fog to simulate the humidity. The leakage current was measured and recorded for comparison with the simulation results. The results of the weather chamber test showed that surface condensation resulted in more severe wetting than manual wetting. The weather chamber surface resistances calculated were much lower than those calculated by the Maxwcll simulations. This was due to the difference it humid particle temperature in the condensation rate equations used for the Maxwell simulations, and the humid particle temperature of the steam fog used in the weather chamber. Polluted coastal outdoor insulators exposed to the above weather conditions will experience larger than normal leakage currents which will lead to premature failure of the units. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2008.

This dissertation describes the impact of changing network configuration on power quality and performance of existing compensation devices in the transmission network. The underlying theory was assessed and thereafter the Everest substation network case scenario was selected to study the above due to; the number of reconfigurations it has experienced in the past, increased capacitor bank failures and also due to the harmonics problems experienced. The study involved the installation of harmonic current measuring instruments at Everest 132kV feeders to identify the potential sources of harmonics and to determine the dominant harmonics. A dig Silent Power Factory model was then constructed to perform various simulations in order to determine the impact of the changes done on the Everest network as well as the impact of capacitor switching on the harmonics amplification at Everest 132kV Bus-bars. The study also focussed on analysing the performance history of the capacitor banks at Everest and to determine if high harmonic amplification had an impact on capacitor bank performance. The simulation results revealed that network reconfigurations have negatively impacted power quality at Everest. The results showed that there is also a correlation between the switching of the two 72MVAR capacitor banks and the amplification of the harmonics at Everest. The highest amplification occurred when both capacitor banks were switched in and the resonance point occurred around the 5th harmonic which coincided with the data from field measurements. There was a 61% increase in 5th harmonic impedance amplitude after the Everest network was reconfigured, for the condition when both capacitors are switched in. The lowest amplification occurred when none of the capacitor banks were switched in. Three options were assessed to eliminate the problem of harmonics at Everest, the first one was to prohibit the switching in of both capacitors at Everest and utilise other available means around the Everest network for voltage support. The second option was to change the capacitor size, thus moving the resonance point away from the 5th harmonic. The last option was to install a harmonic filter at Everest to filter out the problematic harmonics. The first option is recommended as it has been successfully tested, can be readily implemented and is much more cost effective compared to the others. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2012.

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