Gas insulated switchgear (GIS) are essential parts of a safe, robust, and flexible energy system. They are responsible for interrupting short-circuit currents when faults occur, isolating parts of the grid during maintenance or faults, and for redirecting power and changing the grid infrastructure when needed. The most common gas used as an insulation medium in GIS today is sulfur hexafluoride, SF6. However, SF6 is the most potent greenhouse gas in existence with a global-warming potential approximately 25 000 times that of CO2. Replacing this gas would reduce the national and global use of SF6, making GIS-technology more sustainable. The project will obtain fundamental knowledge on discharge behaviour of the alternative gases and gas mixtures through experimental and computational research.
A PhD candidate started at NTNU in the fall of 2021 and is working on experimental characterization and computational modelling of electrical discharges in SF6-alternatives. A setup consisting of a 400 L, 1.5 bar pressure vessel with custom made electrodes has been established and connected to a lightning impulse generator. Advanced high-speed cameras capture the discharge development in the tank with up to 1 billion frames per second. A photo-multiplier tube detects the discharge light emission. The initial tests have been performed in both air and C5-FK gas mixture, and a conference paper on these initial tests has been presented at Nordic Insulation Symposium 2022. In the autumn of 2022, the focus has been to verify a probability-based model for discharges in different gas mixtures. The plan is to continue with these tests in the spring of 2023, in collaboration with simulations, and for this to result in a journal paper. These tests are performed in both air and in a Fluoroketone gas mixture. An abstract on the subject has been submitted to the ISH 2023 conference. There is also ongoing work on planning future experiments that can be performed at ETH Zürich, where the PhD candidate is planning an exchange stay in 2024.