Energizing a high voltage gas-insulated line (GIL) running with an SF₆-free insulating gas mixture is an enormous technical achievement, as acknowledged by the entire electrical transmission industry. Since its introduction in the 1970’s, there has been no alternative to the SF₆ technology as an insulation medium in high voltage (HV) switchgear, until now. GE’s SF₆ alternative insulation medium is called g³: Green Gas for Grid.

On April 13, 2017, National Grid achieved a huge industry milestone with the energization of the first SF₆ -free 420 kV gas-insulated line in their South East England network. The new Sellindge substation was deployed in an operationally critical part of the UK’s transmission network to help ensure the region would continue to benefit from a safe and reliable supply of electricity. It plays a vital role in the ElecLink project, which will increase the UK’s energy security, reliability and capacity by connecting with the French electricity transmission network.

Giuseppe Sottero, General Manager, Gas-Insulated Substations at GE Grid Solutions said, "We are very pleased to collaborate with National Grid on this project, the first in the world to use a g³ solution. Utilities wanting to reduce their global warming potential now have an alternative to SF₆."

Industry framework

In a world of ever increasing power demand, utility companies have a vital role in connecting millions of people safely, reliably and efficiently to the energy they use. Sulfur-hexafluoride (SF₆) is used in the HV electrical transmission industry because it is an excellent gaseous dielectric medium. Unfortunately, it is also the greenhouse gas with the largest global warming potential (23,500 times more than C0₂). Thus, much effort has been made across the industry in the last decades to find a viable alternative. Today, with g³ from GE, the industry is positioned for the next breakthrough in high voltage equipment.

National Grid at the forefront of green technology development

National Grid has made strong commitments to their regulators and stakeholders regarding the ongoing reduction of SF₆ release into the atmosphere. As a group they have set a voluntary target to reduce greenhouse gas (GHG) emissions across their UK and US businesses by 45% by 2020 (baseline: 1990). The introduction of GE’s g³ solution provides an opportunity for National Grid to be at the forefront of new technology development, and obtain an early understanding of the performance of the equipment.

Mark Waldron, Switchgear Technical Leader at National Grid said, "g³ opens the way for reducing or eliminating SF₆, and that’s something that for National Grid is really important."

A drastically reduced global warming impact

Replacing 1 kg of SF₆ with the corresponding mass of g³ helps avoid the equivalent of 16 cars running one year. The potential global warming reduction is important if you look at SF₆ quantities installed worldwide. 10,000 tons are installed each year and 80% are used in the transmission industry.

The estimated gas emissions savings for the Sellindge GIL are huge: more than 11,000 tons of CO₂ equivalent (CO₂e) will be saved during the service life of the 300 meter-long gas-insulated circuits which connect the substation to the bushings and overhead lines.

The environmental achievement does not compromise the technical performance: g³ applications demonstrate the same technical performance, they operate in the same ambient conditions (even down to -25 or -30°C), and they feature the same dimensional footprint.

About g³

g³ is a proven and ready-to-go alternative insulating gas mixture for HV electrical transmission equipment, providing the same technical performance as SF₆ with an environmental impact reduced by more than 98%. The g³ gas mixture is based on 3M™ Novec 4710 molecule from the fluoronitrile family, with a carefully balanced percentage of Carbon Dioxide. It offers an efficient combination of low global warming potential (GWP) with high dielectric performance and minimum operating temperatures in accordance with the typical Transmission System Operators’ (TSO) needs.

g³ is available to all utilities

g³ is fully type-tested and commercially available for GIS up to 145 kV, GIL up to 420kV, and AIS current transformers up to 245 kV.

Six (6) utilities have already decided to implement g³ solutions on their networks and numerous other ones are now considering it with GE.

SF₆ remains in the atmosphere for 3200 years, and its concentration has increased by 20% in the last 5 years alone. The time for change has come. Today there is an alternative to SF₆ for HV switchgear. Installing site applications and supporting the wider adoption of g³ technology is all about corporate and social responsibility. It’s about doing our part to mitigate global warming, and about improving people’s lives.