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Performance of polluted composite insulators for the conversion of selected UK tower lines to HVDC operation under severe pollution conditions

Pinzan, Davide 2021. Performance of polluted composite insulators for the conversion of selected UK tower lines to HVDC operation under severe pollution conditions. PhD Thesis, Cardiff University.
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HVDC systems are increasingly being integrated in electric power systems and one of the main challenges to address relates to outdoor insulation. This thesis provides five main contributions with focus on composite insulators. First, an extensive literature review examines the state of the art of relevant research topics: the need of corona rings in HVDC systems; the influence of non-soluble deposit type on the hydrophobicity recovery; the effect of non-uniform hydrophobicity on flashover voltage; DC pollution severities; optimal creepage design at different severities; and the influence of wind speed on pollution accumulation. Secondly, the HVDC analytical and laboratory characterisation of heavily polluted insulators was performed between 121 and 252 kV. The test results confirmed that the insulators oriented horizontally performed better than vertically, which was attributed to the differences in the arc propagation and in the convection heat direction. Thirdly, new laboratory data was obtained for switching impulse (SI) in the range of 168 to 345 kV and for SI superimposed on a direct voltage of 16 kV. As a conclusion, in most conditions, the HVDC pre�energisation has a negative impact on the flashover performance. Then, with the acquired knowledge and using IEC and CIGRE insulation selection and dimensioning recommendations, proposals to convert three existing UK HVAC towers lines to HVDC operation have been designed between 170 and 500 kV, considering heavy and extremely severe pollution. The results show an increase of 1.6 to 2.9 times in power transfer. It was also confirmed that a few nanoamperes leakage current is sufficient to satisfy the electric field distribution requirements without the use of corona rings. Lastly, a laboratory wind tunnel was built to investigate the insulator pollution accumulation, with the option of HVDC energisation. Promising initial test results were obtained, and future work has been suggested

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Engineering
Uncontrolled Keywords: HVDC overhead line, HVDC outdoor insulation , HVDC polluted insulator, Conversion of overhead line , Wind tunnel polluted insulator , Switching impulse HVDC , HVDC tower , HVDC composite.
Date of First Compliant Deposit: 29 March 2022
Last Modified: 30 Mar 2022 14:02

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