Blue Technology in Switchgear for Sustainable Power Transmission Systems: Dielectric, Switching, Life-Cycle and Techno-Economic Modelling of SF₆-Free Clean-Air and Vacuum Gas-Insulated Substations

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Publication Details

Journal
Research Square
Published
2026-09-22
DOI
https://doi.org/10.21203/rs.3.rs-11089340/v1
Primary Topic
High voltage insulation and dielectric phenomena
Type
preprint
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preprint

Blue Technology in Switchgear for Sustainable Power Transmission Systems: Dielectric, Switching, Life-Cycle and Techno-Economic Modelling of SF₆-Free Clean-Air and Vacuum Gas-Insulated Substations

Mohammad Ali, Mohiddin Abdul Quadir, Md Abu Bakkar Siddique, Kamrun Nahar
Research Square
High voltage insulation and dielectric phenomena
preprint

Blue Technology in Switchgear for Sustainable Power Transmission Systems: Dielectric, Switching, Life-Cycle and Techno-Economic Modelling of SF₆-Free Clean-Air and Vacuum Gas-Insulated Substations

Mohammad Ali, Mohiddin Abdul Quadir, Md Abu Bakkar Siddique, Kamrun Nahar
preprint en

Abstract

Abstract Sulphur hexafluoride (SF₆) has been the reference insulating and arc-quenching medium of high-voltage switchgear for six decades, but with a global warming potential of about 24 300 and an atmospheric residence time of the order of 3 200 years it is now the single largest direct greenhouse-gas liability of the transmission sector. "Blue" switchgear technology — vacuum interruption combined with clean-air (80% N₂ / 20% O₂) insulation — removes fluorinated gases from the substation entirely. This thesis develops an integrated engineering model of blue switchgear for sustainable power transmission and evaluates it against SF₆ and fluoronitrile (C₄-FN) alternatives for a 145 kV, 40 kA reference bay. A streamer-criterion dielectric model with Schwaiger field-utilisation and an empirical design-derating factor yields a clean-air design point of a 150 mm coaxial gap at 6.2 bar absolute for a 650 kV lightning impulse withstand level, against 95 mm at 4.4 bar for SF₆; the enclosure diameter grows from about 300 mm to 475 mm and the bay footprint by roughly 22%. A vacuum-arc recovery model shows a dielectric-recovery rate of approximately 18 kV/µs against a transient recovery voltage of 2.0 kV/µs, giving an interruption margin of about nine. A Rayleigh-number-based thermal model shows that the lower volumetric heat capacity of clean air requires a 28% larger conductor cross-section to hold the temperature rise below 65 K at 2 500 A. A cradle-to-grave life-cycle inventory gives 377 t CO₂-eq for the SF₆ bay against 92 t CO₂-eq for the blue bay, a 75.7% reduction, of which 77% of the SF₆ burden is gas leakage and end-of-life release. A discounted life-cycle cost model with a 9.5% capital premium gives a break-even at service year 19 and a net present advantage of 3.9% of capital cost at 40 years; sensitivity analysis shows that the business case is governed by capital premium, gas-handling and compliance cost, and discount rate, and only weakly by carbon price. A four-layer system architecture linking the primary plant, an IEC 61850 digital layer, an asset and carbon-accounting layer and the regulatory interface is proposed, together with a weighted multi-criteria sustainability index in which blue technology scores 0.89 against 0.73 for the fluoronitrile route and 0.54 for SF₆.

Research Square
Chittagong University of Engineering & Technology (BD), Atlantic International University (US), East–West University (US), Islamic University of Technology (BD)
Responsible consumption and production, Industry, innovation and infrastructure
High voltage insulation and dielectric phenomena
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