A sustainable GIL solution will help to connect offshore renewables to urban centres. Our project will focus on identifying:

• The potential for GIL to provide high-capacity transmission connections over 2000MVA to increase capacity available for new offshore wind generation.
• Options to replace SF6 with alternative low carbon footprint gases as a viable means of GIL insulation. 

Scope: The project meets the scope of the competition by developing and widely implementing a technology that will allow more rapid progress towards Whole System integration and decarbonisation. It will address:

1. “Current and future heat, power, and transport energy requirements”: the solution potentially offers more cost-effective, sustainable and better-performing transmission capacity delivery to support demand growth from heat and transport electrification.
2. Novel approaches to infrastructure investment to maximise efficiency in large-scale network and system investments by taking systems view across generation and demand side changes linked to decarbonisation.

Project Partners

Lead partner is National Grid Electricity Transmission (NGET). Additional project partners are:

• Ørsted as a windfarm developer and generation licence holder.
• Scottish Power Transmission (SPT) and National Grid Electricity System Operator (NGESO) as networks owners and operators.
• General Electric (GE) as the GIL technology provider.
• J. Murphy & Sons as civil construction expert and EPC.
• University of Manchester as an academic partner and expert in HV assets and SF6 replacement.
• Frazer-Nash Consultancy (FNC) as techno-economic assessment experts.

These partners bring knowledge and capabilities and have a strong interest in advancing SEGIL technology: NGET, SPT and Ørsted can deploy the solution on the respective networks, GE will design and produce innovative GIL components, University of Manchester can expand their research in the area of sustainable gases and new assets, J. Murphy & Sons would benefit from learning how to specify, procure, install and commission GIL, while FNC would gain experience collaborating with the networks on innovative technology.

User Needs

Potential users of SEGIL technology are NGET, other transmission owners (TOs) and offshore wind developers that require connection of new offshore generation sites to the existing networks via high-capacity connections; faster and with less disruption to local communities or wildlife. Future power infrastructure investments can benefit from increasing the range of technologies available, including the replacement of existing assets reaching the end of life. The potential benefits to consumers are faster integration of renewable generation and a more cost-effective and sustainable network, with lower impact on areas of natural beauty. 

Problem Bring Solved

Context: The UK Government has committed to achieve Net Zero by 2050 that leads to significant changes in GB energy system:

• An increase in renewable generation with UK government’s commitment to deliver 40GW of offshore wind power by 2030 by large windfarms on the East Coast where the transmission network is underdeveloped for the expected connection capacity.
• Decarbonisation through electrification of heat and transport which will significantly increase the demand for electricity, especially in heavily populated areas. 

Problem: The increasing need to transmit electricity from offshore renewables to urban centres where demand is growing requires new efficient, resilient, cost-effective and rapidly deployable solutions. Without this, offshore wind energy integration and ultimately the UK’s Net Zero targets may be compromised.

Despite radical grid advancements elsewhere, the core transmission technology, high-capacity high voltage (HV) overhead line (OHL) has remained largely unchanged in past decades. However, public opposition to the visual impact of OHLs and impacts on wildlife, lead to challenges with planning consents, design and build. Relying on conventional OHL lead to a risk not delivering required capacity quickly enough to accommodate fast-growing demand in cities.

Underground HV cable systems offer low visual impact and often receive consent much faster. However, they too bring challenges:

• They are more costly and require significant construction works.
• Operational challenges, as in the case of an internal fault, a circuit stays out of service for significantly longer due to identifying faults, excavation and replacement.

Solution: This project would begin early-stage R&D by exploring opportunities for a new alternative – Gas Insulated Line (GIL), in certain way similar to a gas transmission, can transmit over 3000MVA, more power than a conventional OHL, and with less construction works than a cable system for the same power rating, hence reducing the cost and time to deliver capacity. However, to develop GIL at scale as a viable alternative, two key challenges must be resolved: 

• Lack of experience with long-distance GIL construction and operation. Currently, the longest operating circuit is 17 km, 420 kV inside a substation.
• Current generation GIL are filled with a sulphur hexafluoride (SF6), a potent greenhouse gas which is 23,900 times more environmentally damaging than CO2. 

The key aim of this Discovery project is to evaluate these challenges and propose solutions to develop a viable, efficient long-distance GIL for high-capacity lines for the GB network.