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Insulator aging tests with HVAC and HVDC excitation using the tracking wheel tester

dc.contributor.advisorVermeulen, H. J.en_ZA
dc.contributor.advisorVosloo, W. L.en_ZA
dc.contributor.authorLimbo, Beulah Sepoen_ZA
dc.contributor.otherUniversity of Stellenbosch. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
dc.date.accessioned2009-11-25T14:04:03Zen_ZA
dc.date.accessioned2010-06-01T08:51:24Z
dc.date.available2009-11-25T14:04:03Zen_ZA
dc.date.available2010-06-01T08:51:24Z
dc.date.issued2009-12en_ZA
dc.identifier.urihttp://hdl.handle.net/10019.1/2529
dc.descriptionThesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2009.
dc.description.abstractENGLISH ABSTRACT: Limited research results are available on the aging impacts of surface discharges for High Voltage Direct Current (HVDC) excitation on practical insulators using the Tracking Wheel Tester (TWT) methodology. This thesis gives details of an experimental investigation to compare the aging performance of insulator samples using the TWT for High Voltage Alternating Current (HVAC) and positive and negative polarity HVDC excitation. Two series of tests were performed. The first series of tests evaluated the aging of six insulator rods, namely three Room Temperature Vulcanized Silicone Rubber (RTV SR) coated glass samples and three uncoated glass samples. Three creepage distances were used for each of the test materials, namely 277 mm, 346 mm and 433 mm. The tests were conducted with HVAC excitation and the test methodology described in the IEC 61302 standard. The second series of tests involved the testing of actual insulator samples. The test voltage and conductivity of the salt water solution were also adapted. Six insulators from different manufacturers, representing different materials and specific creepage distances, were tested with HVAC and positive and negative polarity HVDC excitation. The test samples consisted of Ethylene Propylene Diene Monomer (EPDM), High Temperature Vulcanized Silicone Rubber (HTV SR), porcelain and SR coated porcelain insulators. The aging performance of the different test samples for the three types of excitation are compared in terms of peak leakage current, visual observations of surface degradation and hydrophobicity properties. The leakage current data for HVAC excitation shows that the insulators from the different manufacturers perform differently, even for the same type of material. The results also indicate differences in the way the surfaces degrade, as well as the rate of degradation. For insulators representing the same specific creepage distance, but different materials, it has been shown that the material does influence the aging performance. Comparison of the leakage current data for the HTV SR insulators from the same manufacturer, but with different specific creepage distances, shows that the specific creepage distance affect the aging performance significantly. In general, the test insulators showed higher peak leakage currents with HVDC excitation compared to HVAC excitation. The results for positive polarity HVDC excitation show that the dry band arcing, as well as the discharges, has the same form for all six insulators. The colour of the dry band discharges ranged from a blue-ish orange to a dark yellow, depending on the intensity of the leakage currents. The hydrophobic insulators, namely the HTV SR, EPDM and RTV SR coated porcelain insulators, had lost hydrophobicity within the first week of testing. The results for negative polarity HVDC excitation show severe surface degradation compared to the results for HVAC excitation. The effect of positive polarity HVDC excitation, however, seems to be more severe in terms of leakage currents and aging compared to negative polarity HVDC excitation.en_ZA
dc.language.isoenen_ZA
dc.publisherStellenbosch : University of Stellenbosch
dc.subjectInsulator testingen_ZA
dc.subjectAgingen_ZA
dc.subjectRotating wheel testen_ZA
dc.subjectPollutionen_ZA
dc.subjectDissertations -- Electrical and electronic engineeringen
dc.subjectTheses -- Electrical and electronic engineeringen
dc.subjectElectric insulators and insulation -- Testing
dc.subjectSurface discharges (Electricity)
dc.titleInsulator aging tests with HVAC and HVDC excitation using the tracking wheel testeren_ZA
dc.typeThesisen_ZA
dc.rights.holderUniversity of Stellenbosch


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