Abstract
The research in this paper consists of practical experimentation on a gas insulated section of high voltage equipment filled with carbon dioxide and technical air as a direct replacement to sulphur hexafluoride (SF6) and analyses the results of PD measurement by way of internal UHF sensors and external HFCTs. The results contribute to ongoing efforts to replace the global warming gas SF6 with an alternative such as pure carbon dioxide or technical air and are applicable to mixtures of electronegative gases that have a high content of buffer gas including carbon dioxide. The experiments undertaken involved filling a full-scale gas insulated line demonstrator with different pressures of CO2 or technical air and applying voltages up to 242 kV in both clean conditions and particle contaminated conditions. The results show that carbon dioxide and technical air can insulate a gas section normally insulated with SF6 at phase-to-earth voltage of 242 kV and that both HFCT and UHF sensors can be used to detect partial discharge with natural gases. The internal UHF sensors show the most accurate PD location results but external HFCTs offer a good compromise and very similar location accuracy.
Highlights
In the high voltage power industry sulphur hexafluoride (SF6 ) is currently used to insulate high voltage equipment worldwide such as gas insulated transmission lines (GIL) and gas insulated switchgear (GIS)
For each gas and pressure described of each partial discharge (PD) event at either the ultra high frequency (UHF) sensors or the high frequency current transformer (HFCT)
The results of the practical research conducted in this paper show that CO2 and technical air can be used to insulate a gas section normally insulated with SF6 at phase-to-earth voltages of 242 kV at a similar pressure to SF6 ; increased pressure is likely to reduce the amount and impact of PD and increase the longevity and lifetime of the equipment
Summary
In the high voltage power industry sulphur hexafluoride (SF6 ) is currently used to insulate high voltage equipment worldwide such as gas insulated transmission lines (GIL) and gas insulated switchgear (GIS). High voltage equipment manufacturers and research institutions worldwide have been trying to find a suitable alternative to replace SF6 in all current equipment required for use in the energy sector. Present solutions are focused on the use of natural gases such as carbon dioxide, nitrogen or technical air at higher pressures to match the insulation and interruption capability of SF6 or the use of electronegative gas mixtures with high mixture ratios of the same natural buffer gases [4,5,6,7,8,9]
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