SF6 greenhouse gas replacement & Low Power Instrument transformer in High Voltage Gas Insulated Switchgear for onshore & offshore substations

PROJECT DESCRIPTION

BACKGROUND

Sulphur hexafluoride (SF6) is an extremely powerful greenhouse gas (GHG): 1 kg of SF6 has the same impact as 23 500 kg of carbon dioxide (CO₂).  Over the last ten years, its concentration in the atmosphere have shown an increase of 45% . Furthermore, due to the growing demand for electricity and the transition to renewable energy sources, the demand for SF6 in medium and high voltage switchgear is expected to increase further. The electricity industry uses SF6 in gas-insulated substations (GIS), enabling the transmission system to handle the high voltages carried between power plants and customer load centres. Disconnectors and ground switches use SF6 primarily for insulation, and individually contain only slightly less SF6 than a circuit breaker, which is the equipment containing the most important volume of SF6. These devices are used to isolate parts of the transmission system where the flow of current has been interrupted (with a circuit breaker). For decades, the electricity grid was a one-way street, with power flowing from large, centralised power stations to customers. But the advent of solar power generation, battery storage, electric vehicles and the growing number of "prosumers" - customers who produce energy as well as consuming it - has introduced a two-way flow with new layers of complexity for grid operators. In addition, the grid must be perfectly balanced, with supply and demand closely matched to avoid system failures. Balancing production and demand to the nearest millisecond and instantly absorbing any unexpected event without interrupting supply is a real challenge. Digitalisation will increasingly become an important part of building a more resilient and robust network. In addition, the digital solution implemented on the instrumentation transformer allows for significant savings in raw materials, mainly copper and steel.

OBJECTIVES

LIFE SF6-FREE GIS aims to combine an economically-sustainable and climate-friendly alternative gas to SF6 and a digital approach for current/voltage transformers. This will be achieved with a new gas-insulated substation (GIS) suitable for both onshore and offshore applications up to 245 kV / 63 kA. The solution will facilitate a move towards complete elimination of SF6 in GIS up to 420 kV, which is the maximum voltage in Europe.

The project has several specific objectives:

• Pilot of 245 kV / 63 kA GIS full bay at GE Grid Solutions’ premises. The objective is to meet Transmission System Operators (TSOs) requirements for a full GIS as required before any on-site installation on a High Voltage transmission network. To achieve this, the project aims to:

1. Carry out a pre-study based on simulation and investigation tests (dielectric and temperature modelling with the composiof the g3-based mixture, specific tests on a model).
2. Adapt the design of the GIS to ensure the 245 kV / 63 kA requirement in a limited size (insulator, disconnector, earthing switches, maintenance devices, passive and connexion components) that meets offshore requirements.
3. Perform the technical validation of the solution to propose and deliver this new compact 245 kV / 63 kA GIS to customers.
4. Integrate all technical and industrial requirements into the design of the new 245 kV GIS to ensure a solution that is suitable for all HV GIS applications and grid needs for the next 15 years.

• Launch of a demonstration at a TSO's premises to implement an integrated 245 kV SF6-free GIS solution on the transmission network. The project team will demonstrate the SF6-free 245 kV GIS bay at one onshore and one offshore site among the following potential TSO sites:

1. Onshore applications: REE (Spain) and RTE (France), which represent the largest networks in Europe for 245 kV GIS.
2. Offshore applications: Orsted (Denmark), Ocean winds (Spain), Equinor (Norway) and Vatenfall (Sweden).
3. Reaching a reduction of 99% of the CO₂eq emissions for the newly installed GIS.

RESULTS

Expected results:

• A 245 kV / 63 kA GIS pilot, based on a combination of an economically-feasible and climate-friendly alternative to SF6 and digitalisation of current/voltage transformers.
• Demonstration that the pilot GIS meets Transmission System Operator (TSO) requirements for onshore and offshore electricity generation.
• In total, approximately 310 tonnes of CO2e saved during the project and test campaigns. After the project, approximately 800 tonnes of CO2eq will be saved per 245 kV GIS bay manufactured..