Strategic Transmission Planning for Great Britain Using Future Operational Scenarios: A new methodology to evaluate and plan UHV links for a clean, secure, and affordable electricity system

Global commitments to net-zero emissions, combined with rising electricity demand, are driving the need for unprecedented expansion of transmission infrastructure. In Great Britain, this transformation is essential to meet future energy needs, integrate large-scale renewable generation, and achieve climate targets. Current transmission infrastructure, largely built in 1960s on a north-south axis to serve historical fossil fuel power stations, is increasingly misaligned with the locations of renewable generation, particularly offshore wind farms in the North Sea. As energy demand grows and generation shifts geographically, strategic expansion and reinforcement of the high-voltage network, including consideration of Ultra-High Voltage (UHV) and high-voltage direct current (HVDC) technologies, is critical.

This report presents a comprehensive methodology for transmission investment appraisal, capable of evaluating the operational value of potential network upgrades across the entire year. Over 50,000 operational scenarios have been developed, spanning different FES pathways, demand profiles, carbon and gas price assumptions, wind conditions, and system flexibility levels, covering the period up to 2050. These scenarios capture the variability and uncertainty inherent in a future low-carbon electricity system, allowing a rigorous assessment of network constraints, locational marginal prices, curtailment, and dispatch costs.