Technologies containing SF6 are widely used in electricity networks, mostly at Medium Voltage (MV) and Low Voltage (LV) levels. These technologies are used in switchgear to isolate and protect different sections of the grid such as switchboards, circuit breakers, metal-enclosed switchgear, and gas-isolated switchgear, amongst others. SF6, according to the USA Intergovernmental Panel on Climate Change, has the highest global warming potential (GWP), 23000-25000 times higher than CO2. The gas also has an atmospheric lifetime of 3200 years. According to Schneider Electric, over 30 million units worldwide of MV switchgear use SF6, and 10 million of these units are in the EU Member States, containing in total more than 8600 tons of SF6.
Highlights
The electricity distribution and transmission systems are responsible for 80% of SF6 emissions. According to the LIFE SF6-FREE HV BREAKER project, considering only HV lines, 33 tons of SF6 are released across Europe every year. The new F-Gas Regulation will introduce a full ban for MV switchgear relying on F-gases, with a gradual phase-out by 2030, and a ban for HV switchgear by 2032.Challenges and opportunities for DSOs
Opportunities:
- Contributing to the reduction of greenhouse gas emissions.
- Potential to develop innovative solutions.
Challenges:
- Market Availability. Not enough switchgear manufacturers with SF6-free solutions are available on the market compliant with the F-gas Regulation. Hence, insufficient production capacities will lead to delays in grid expansion.
- Potential cost increase on new technology purchasing, existing infrastructure upgrading, installation, maintenance and training.
- Finding current SF6 equipment replacements with similar performance characteristics.
- Maintenance of existing SF6-based installations until the end of their lifetime.
EDSO Considerations
- DSOs are committed to the transition to an SF6-free grid.
- It is necessary to have a close interaction with the equipment manufacturers so that the development and deployment of SF6-free solutions can be accelerated and addressed in an effective way.
- All technical grid equipment, including switchgear and circuit breakers, must meet strong reliability criteria throughout their entire life cycle. With this, any future SF6 solution must be proven to be as reliable, cost-effective, and safe as currently deployed SF6-based technology.
- Research and experimentation between transmission and distribution equipment manufacturers and end-users on SF6-free solutions should be enhanced.
Potential use cases
- Air-insulated Switchgear (AIS). Usage of air as insulation medium instead of SF6 in circuit breakers, disconnect switches, and busbars, amongst others.
- Gas-insulated Switchgear (GIS). Alternative gases such N2 and a mixture of dry air and synthetic gases are being used as insulation gases instead of SF6.
- Solid-insulated Systems (SIS). Solid insulation materials can replace SF6 in some applications due to their electric insulation properties.
- Vacuum-insulated Switchgear (VIS). Usage of a vacuum environment as an insulation medium instead of SF6. As an example, on circuit breakers, the arc extinction and current interruption are done in a vacuum environment. VIS is a viable option since it offers good insulation properties.
Ongoing projects
- LIFE SF6-Free is deploying SF6-free MV switchgear pilot installations and developing innovative MV SF technology with Shunt Vacuum Interruption (SVI) (more info).
- LIFE SF6-Free HV Breaker aims at combining a viable gas alternative to 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 (more info).
- Enedis is carrying out experimentation works on SF6-free alternative solutions. These works allow the qualification of alternative solutions to SF6, such as AIS for higher voltage primary substations with vacuum interruption. Furthermore, Enedis no longer installs new electrical 24 kV switchboards with SF6 in its primary substations since 2021.
- E-REDES has been testing various SF6-free solutions together with manufacturers and technology providers since 2021.
- A new type of SF6-free MV switchgear with vacuum switching and solid insulation media (up to 24kV) is being tested in the framework of the NextStep project, serving as the test bed for E-REDES’ first SF6-free MV secondary substation switchgear integrated with Internet of Things (diagnosis of insulation condition and MV condition).
- An SF6-free secondary substation protection is being tested in three 15/10kV secondary substations to validate the technological performance of a secondary distribution cell without SF6 with remote control and integrated network protection.
- Another pilot is being performed on a 15/10kV secondary substation to validate the technological performance of an SF6-free secondary distribution cell with integrated remote control.
- The technological performance of a primary distribution cell without SF6 as an alternative to the current AIS is being validated in a 60/30kV substation and a 15/10kV secondary substation.
- E-REDES is also evaluating HV alternative solutions to comply with regulatory provisions for the technological phase-out of SF6 solutions.
- E-REDES Spain is testing various SF6-free solutions.
- Remote-controlled modular cells with vacuum cut-off technology integrated into the MV distribution network.
- SF6-free modular line cells sewn to an SF6 protection cubicle in a transformer substation.
- SF6-free modular protection cabinets.
- Automated secondary distribution MV switchgear with dry air insulation and vacuum cut-off technology.
- Enel is currently trialling, mainly in Spain and Italy, SF6-free equipment both at the MV (up to 24KV) and HV levels (up to 145KV). During 2019 and 2020, thanks to an open innovation approach, Enel involved two of the main suppliers of MV and HV equipment in developing SF6-free projects in compliance with their current technical requirements. The installation of twenty MV Ring Main Units (RMU) at 24 kV with alternative gas insulation was conducted in Italy and Spain, while five HV circuit breakers at 145 kV with dry air insulation were installed in Spain.
- E.ON grid operators are currently running different pilot projects at MV and HV levels using dry air and vacuum for insulation and braking respectively.
- i-DE is currently testing SF6-free equipment at MV (on secondary substations at 24 kV) and HV (on primary substations at 132 kV) in collaboration with different manufacturers with the purpose of developing and reaching market maturity for these products.
- At the MV level, a complete primary substation has been installed with ‘AirPlus’ technology and an existing primary substation has been enlarged with two dry air insulated switch panels (both operating at 24 kV).
- On higher voltage levels (i.e. at 110 kV), two SF6-free switch panels have been installed with a 145 kV dry insulation with a vacuum circuit breaker respectively, complemented by dry air instrument transformer sets enabling remote online performance monitoring.
- MV trials use dry air with vacuum breaking, while HV trials use an alternative fluorine gas.
- Available SF6-free technologies are being analysed, but none of them have been found ready for a successful implementation on the network yet.
- i-DE has been committing to the verified end-of-life management of SF6 switchgear since the mid-90s, providing recycled SF6 for maintenance.
Last update: 17 May 2024