An integrated framework for systematically identifying optimal high-voltage transmission routes in renewable energy systems

Global commitments to net-zero emissions and rapid electrification require unprecedented, fast transmission expansion, yet most planning methods still rely on simplified models or incremental upgrades that overlook the complex interplay of renewable resource availability, grid balancing needs, and challenges of routing lines across vast terrains. In this paper, we present an integrated transmission expansion planning framework that couples system balancing optimization with high-resolution Geographic Information System analysis to capture both strategic and tactical constraints in one model. Using the Australian electricity system as a case study, the framework identifies new high-voltage alternating-current lines that can unlock large amounts of geographically optimal solar and wind resources while enhancing reliability, and targeted long-distance high-voltage directcurrent links that cut system cost by up to 18 % by bridging winter supply-demand gaps. The results reveal several priority corridors and connection points capable of accelerating large-scale uptake of renewables in Australia, and the method is readily transferable to other regions facing similar decarbonisation challenges.