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  • 1
    Publication Date: 2019
    Description: Creeping discharges over insulator surfaces have been related to the presence of triple junctions in compressed gas insulated systems. The performance of dielectric materials frequently utilised in gaseous insulating high voltage applications, stressed under triple junction conditions, has been an interesting topic approached through many different physical perspectives. Presented research outcomes have contributed to the understanding of the mechanisms behind the related phenomena, macroscopically and microscopically. This paper deals with the electrical detection of creeping discharges over disc-shaped insulator samples of different dielectric materials (polytetrafluoroethylene (PTFE), epoxy resin and silicone rubber) using atmospheric gases (dry air, N2 and CO2) as insulation medium in a point-plane electrode arrangement and under AC voltage application. The entire approach implementation is described in detail, from the initial numerical field simulations of the electrode configuration to the sensing and recording devices specifications and applications. The obtained results demonstrate the dependence of the generated discharge activity on the geometrical and material properties of the dielectric and the solid/atmospheric gas interface. The current work will be further extended as part of a future extensive research programme.
    Electronic ISSN: 1996-1073
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by MDPI
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  • 2
    Publication Date: 2018-08-07
    Description: Energies, Vol. 11, Pages 2037: Evaluation of SF6 Leakage from Gas Insulated Equipment on Electricity Networks in Great Britain Energies doi: 10.3390/en11082037 Authors: Phillip Widger Abderrahmane (Manu) Haddad This paper examines the data collected from the power industry over the last six years of actual reported emissions of sulphur hexafluoride (SF6) and the potential impact. The SF6 emissions have been collated from the 14 different regions in England, Scotland, and Wales (Great Britain) from the six distribution network operators. The emissions of SF6 due to the transmission network of Great Britain have also been collated from the three different transmission network operators. By collecting this SF6 emissions data from the power industry, in both the distribution and transmission networks, an overall view of the scale of SF6 emissions in Great Britain can be evaluated. Data from the power industry also shows the inventory of SF6 power equipment in use over the last six years in Great Britain and shows the calculated percentage leakage rate of all of this equipment. In this paper, these figures, as reported by the electrical power industry to the UK government, have been used to estimate the likely inventory of SF6 equipment in England, Scotland, and Wales by 2050 and the future emissions of SF6 that could be leaked into the atmosphere by this equipment.
    Electronic ISSN: 1996-1073
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by MDPI Publishing
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  • 3
    Publication Date: 2020-06-05
    Description: This paper uses practical experimentation to analyse the effect of replacing SF6 with pure CO2 in conventional gas insulated transmission line sections by studying partial discharge measurements taken with applied voltages up to 242 kV (rms). The results can also help in understanding the properties of new alternative gas mixtures which can be utilised with a ratio of up to and over 95% CO2. The experiments undertaken involved filling a gas insulated line demonstrator with 3 bars of CO2 and applying voltages up to 242 kV in both clean conditions and particle-contaminated enclosure conditions. The results demonstrate that CO2 can be used to insulate gas equipment without breakdown at high voltage, however, a higher gas-filling pressure may be needed to reduce the partial discharge found in the tests presented in this paper. Another aspect of the work showed that partial discharge (PD) measurements from internal ultra-high frequency (UHF) sensors compared with a direct measurement from a capacitive divider both clearly showed the effect of contaminating particles in CO2. However, the PD divider measurements also showed considerable external PD on the outside of the gas compartment, leading to the conclusion that UHF sensors are still regarded as having the highest sensitivity and noise immunity for gas insulated switchgear (GIS) or gas insulated transmission line (GIL) systems including when the equipment is insulated with CO2.
    Electronic ISSN: 1996-1073
    Topics: Energy, Environment Protection, Nuclear Power Engineering
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  • 4
    Publication Date: 2020-08-09
    Description: 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.
    Electronic ISSN: 1424-8220
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
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  • 5
    Publication Date: 2019-04-23
    Description: Increasing demand for an alternative insulation medium to sulphur hexafluoride (SF6) has led to the investigation of new environmentally friendly insulation gases which could be used in high voltage equipment on the electrical power network. One such alternative, which is currently being explored by researchers, is Trifluoroiodomethane (CF3I) which could potentially be used in a gas mixture with carbon dioxide (CO2) as an insulation medium. In this paper an analysis of gaseous by-products detected as a result of high voltage breakdown through pure CF3I and a CF3I-CO2 gas mixture across a sphere-sphere electrode arrangement is given. Gas chromatography and mass spectrometry (GCMS) is used to identify the gaseous by-products produced as a result of high voltage arcing which causes the gas between the electrodes to dissociate. Analysing these gas by-products helps to identify the long-term behaviour of the gas mixture in high voltage equipment.
    Electronic ISSN: 1420-3049
    Topics: Chemistry and Pharmacology
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  • 6
    Publication Date: 2019-08-01
    Description: Creeping discharges over insulator surfaces have been related to the presence of triple junctions in compressed gas insulated systems. The performance of dielectric materials frequently utilised in gaseous insulating high voltage applications, stressed under triple junction conditions, has been an interesting topic approached through many different physical perspectives. Presented research outcomes have contributed to the understanding of the mechanisms behind the related phenomena, macroscopically and microscopically. This paper deals with the electrical detection of creeping discharges over disc-shaped insulator samples of different dielectric materials (polytetrafluoroethylene (PTFE), epoxy resin and silicone rubber) using atmospheric gases (dry air, N2 and CO2) as insulation medium in a point-plane electrode arrangement and under AC voltage application. The entire approach implementation is described in detail, from the initial numerical field simulations of the electrode configuration to the sensing and recording devices specifications and applications. The obtained results demonstrate the dependence of the generated discharge activity on the geometrical and material properties of the dielectric and the solid/atmospheric gas interface. The current work will be further extended as part of a future extensive research programme.
    Electronic ISSN: 1996-1073
    Topics: Energy, Environment Protection, Nuclear Power Engineering
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  • 7
    Publication Date: 2018-08-06
    Description: This paper examines the data collected from the power industry over the last six years of actual reported emissions of sulphur hexafluoride (SF6) and the potential impact. The SF6 emissions have been collated from the 14 different regions in England, Scotland, and Wales (Great Britain) from the six distribution network operators. The emissions of SF6 due to the transmission network of Great Britain have also been collated from the three different transmission network operators. By collecting this SF6 emissions data from the power industry, in both the distribution and transmission networks, an overall view of the scale of SF6 emissions in Great Britain can be evaluated. Data from the power industry also shows the inventory of SF6 power equipment in use over the last six years in Great Britain and shows the calculated percentage leakage rate of all of this equipment. In this paper, these figures, as reported by the electrical power industry to the UK government, have been used to estimate the likely inventory of SF6 equipment in England, Scotland, and Wales by 2050 and the future emissions of SF6 that could be leaked into the atmosphere by this equipment.
    Electronic ISSN: 1996-1073
    Topics: Energy, Environment Protection, Nuclear Power Engineering
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  • 8
    Publication Date: 2020-11-12
    Description: In electrical networks, SF6 gas is currently used to insulate high-voltage equipment, however, due to its high environmental impact, new alternatives such as CO2 and electronegative gas mixtures such as CF3I-CO2 are being trialled to replace SF6 and create a sustainable energy system. A high-voltage lightning impulse (1.2 μs/50 μs) was used to approximate the disturbance in a high-voltage electrical network caused by a lightning strike and helped to identify the likely streamer and leader formations in different gases insulating a piece of gas insulated switchgear. In this paper, the theoretical and practical aspects of electrical streamer and leader formations in pure CO2 and an electronegative gas mixture of CF3I-CO2 are examined using schlieren videography in small length rod-plane gas gaps between 20 and 50 mm in length. Schlieren allows the examination of gas density in streamer formations and for the differences in weakly attaching gases, such as CO2, and electronegative gas mixtures, such as CF3I-CO2, to be studied. The gas pressure is varied in order to examine the differences in streamer and leader formation as the gas density is varied and hence the probability of electron collision is varied.
    Electronic ISSN: 2076-3417
    Topics: Natural Sciences in General
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