SF6 greenhouse gas replacement in outdoor high voltage circuit breakers

PROJECT DESCRIPTION

BACKGROUND

Although it has excellent insulator and arc extinguisher properties for High Voltage (HV) applications, sulphur hexafluoride (SF6) is the most potent and persistent greenhouse gas. SF6 has a 23 500 times higher global warming potential (GWP) than CO₂ over 100 years and an atmospheric lifetime of 3 200 years. The potential for emission reduction in the HV industry is highlighted by the quantity of SF6 installed worldwide: considering only 245 kV / 420 kV / 550 kV rating voltage, 165 tons of SF6 are filled-in within HV live tank circuit breakers (HVLTCB) every year. Among them, 33 tons of SF6 are released across Europe, emphasising the importance of looking for good viable alternative dielectric gases to meet the EU's climate goals. This is clearly reflected in the European F-gas Regulation (EC 517/2014), which aims at cutting the EU’s F-gas emissions by two-thirds by 2030. The concrete goals are: i) limiting the total amount of the most important F-gases that can be sold in the EU from 2015 onwards, in order to phase out up to one-fifth of 2014 sales by 2030 and to drive research and industry towards investment in alternatives; ii) banning the use of F-gases in many new types of equipment, and iii) preventing emissions of F-gases from existing equipment by proper monitoring, staff certification and recovery of the SF6 at the end of the equipment's life.

OBJECTIVES

The LIFE SF6-FREE HV BREAKER project aims at combining a viable, climate-friendly green gas alternative for SF6 with an improved interrupting unit technology suitable for an outdoor high voltage live tank circuit breaker (HVLTCB) operating from 245 kV/50 kA to 550 kV/50 kA. The project will focus on Air Insulated Switchgear (AIS), because it is has a large market, hence impacts in term of CO₂ eq. greenhouse gas emission savings will be significant. The project aims to harness the knowledge acquired in the use of g³-based gas mixtures in various switchgear components, and to translate it to 245 kV/50 kA HVLTCB for AIS, hence drastically reducing the use of SF6.

Specific objectives are to:

• Set-up of a pilot 245 kV/50 kA HVLTCB at Grid Solution (GE) premises to meet transmission system operators (TSOs) requirements for HVLTCB, as required before any on-site installation on a HV transmission network;
• Validate the technical viability of the combination of the new gas mixture based on g³ technology and the improved 245 kV/50 kA HVLTCB design;
• Launch a demonstration at a TSO premises to implement an integrated 245 kV/50 kA SF6-free HVLTCB solution on the transmission network;
• Integrate 420 kV/50 kA and 550 kV/50 kA technical requirements in the new HVLTCB design in order to guarantee a solution fitting the whole HV AIS applications.
  

LIFE SF6-FREE HV BREAKER addresses the urgent need for replacing SF6 in electrical switchgears and HV applications. This approach falls under a selected policy priority, as it helps implement the Kigali Amendment and the EU Regulation ((EU) No 517/2014) on reducing the use of fluorinated greenhouse gases.

RESULTS

Expected results:

• Reduction of 63% of the CO₂ eq. emissions: in total, 191 tons CO₂ eq. emission savings will be achieved with the building of 14 (245 kV) circuit breakers and 8 pole prototypes;
• After the project, 7.1 tons CO₂ eq. will be saved per 245 kV HVLTCB manufactured and 2.5 tons CO₂ eq. per year of use of the innovative and enhanced g³ HVLTCB developed by the project team;
• In addition, an average amount of 3.4 kg SF6 is released into the atmosphere during the lifecycle (40 years) of each single SF6-insulated 245 kV HVLTCB installed by GE and 7.5 kg SF6 for 420 kV circuit breaker (equipment leakage, maintenance, and decommissioning). Therefore, replacing SF6 by g³ could save another 80 to 175 kilotons CO₂ eq. emissions for every HVLTCB.