Dual-gas solution for 420 kV Gas-Insulated Substation (GIS) compatible with SF₆ and SF₆-free gas

Climate change is becoming a key challenge of this century and grid operators across the world are becoming increasingly concerned about the environmental impact of their assets and are putting in place many actions to reduce the effects of global warming. This is also supported by reinforced environmental policies by government to reduce greenhouse gas emissions.SF <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</inf> is also listed as an extremely potent greenhouse gas according to the Kyoto protocol and all T&D equipment manufacturers are actively working to replace it in high voltage products. Regulations like F-gas in Europe are under revision to accelerate this transition. Among various SF <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</inf> -free alternative solutions, C4FN gas mixture has shown the ability to replace SF <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</inf> for GIS applications up to the highest ratings like 550 kV rated voltage and 63 kA short circuit.During this period of on-going discussions on revision of regulations, some users are delaying their transition to SF <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</inf> -free solutions, while others are continuing investment in SF <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</inf> switchgears, putting additional tons of SF <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</inf> on their assets for the next decades. Best approach for manufacturers of SF <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</inf> -free equipment like gas-insulated substations (GIS) is to design and install modular solutions and ready to be adapted to coming SF <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</inf> -free demand.C4FN gas mixture has similar behavior than SF <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</inf> , allowing achievement of same ratings with same size of GIS. The aim of this paper is to introduce the dual gas concept and present the ability of new GIS products above 52 kV to be filled with SF <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</inf> or with C4FN gas mixture with a focus on 362/420 kV GIS.