Calculation Method for Carbon Emissions of Ultrahigh Voltage Substation and Converter Station Construction Based on Hybrid Life Cycle Assessment

Amid China's intensive development of Ultra-High Voltage (UHV) transmission networks, the carbon emission issues resulting from energy, construction materials, and equipment consumption during UHV project construction have garnered significant attention. To accurately assess the carbon emissions associated with UHV project construction, this paper proposes a methodology based on the Hybrid Life Cycle Assessment Method. The carbon emission sources from the construction of UHV substations and converter stations are classified into traceable and non-traceable carbon emission groups according to their emission characteristics. The Process-based Life Cycle Assessment method is applied to the traceable emissions, while the Input-Output Life Cycle Assessment method is used for the non-traceable emissions, enabling a comprehensive quantification. Finally, to validate the scientific rigor and feasibility of this model, the carbon emissions during the construction phase of two substations and one converter station were calculated to be 292,000 tons, 274,000 tons, and 793,000 tons, respectively. The carbon emissions are found to be proportional to the complexity and functional requirements of the structures. The primary carbon emission sources during the construction phase are construction materials and equipment manufacturing, accounting for over three-quarters of total emissions. Construction activities, equipment installation, and other engineering operations are relatively minor, but still make a significant contribution to the overall carbon footprint.