Eco-friendly gas insulating medium for next-generation SF6-free equipment

Gas-insulated equipment (GIE) is widely used in the power industry, relying on sulfur hexafluoride (SF6) as insulation and arc-quenching medium. However, SF6 is a potent greenhouse gas with a high global warming potential and long atmospheric lifetime. To address the “net-zero” goal and sustainable development, a research team led by Xiaoxing Zhang of Hubei University of Technology in China, along with scientists from various universities and Schneider Electric, has reviewed the advancements in eco-friendly gas insulating mediums for next-generation SF6-free equipment. The review was published in the journal iEnergy on March 31, 2023.

The report begins by introducing SF6-based GIE, discussing emission and reduction policies to emphasize the need for eco-friendly alternatives. Prof. Zhang explains that SF6 is a major contributor to greenhouse gas emissions, particularly in the power industry, where it is consumed in large quantities in China and globally. Due to environmental concerns, countries have implemented regulations on the use, recovery, and treatment of SF6, driving the demand for eco-friendly insulating gases.

The review outlines the essential requirements for eco-friendly gases, including environmental features, insulation and arc-quenching performance, stability, material compatibility, and biosafety. Various categories of eco-friendly gases are introduced, such as traditional gases (CO2, N2, air), perfluorocarbons, trifluoroiodomethane, fluorinated nitriles, fluorinated ketones, and hydrofluoro-olefins. The molecular design method for eco-friendly gases is also discussed.

The review highlights recent progress in eco-friendly insulating gases, focusing on dielectric insulation, arc-quenching properties, stability and decomposition, materials compatibility, and biosafety. The application of these gases in medium-voltage and high-voltage scenarios, as well as relevant maintenance-related technologies, is summarized. Notably, GE and ABB have developed C4F7N/CO2 and C5F10O/air-based gas insulated switchgear, transmission lines, and ring main units since 2016. There is also interest in fluorinated-free technology that combines technical air with vacuum interruption.

Despite significant efforts in the field, several challenges remain in achieving next-generation SF6-free GIE. These challenges include improving stability, interruption capacity, and material compatibility. Additionally, effective SF6 control and recycling, insulation coordination, and scientific management of perfluoroalkyl substances (PFAS) are vital for the development of eco-friendly insulating gases and GIE.

Source: Tsinghua University Press

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