Carbon Emission Accounting Method for Ultra-High Voltage Transmission Line Construction Considering Carbon Intensity and Activity Data Uncertainty
Ultra-high voltage (UHV) transmission lines are critical infrastructure for China's energy strategy. Compared with conventional voltage lines, UHV lines exhibit nonlinear growth in resource and capital consumption, complex supply chains, and strong spatiotemporal heterogeneity in carbon emission factors, resulting in substantial and uncertain construction-phase emissions. Accurate accounting is essential for achieving carbon peaking and carbon neutrality goals in the power sector. To address issues of ambiguous system boundaries, weak characterization of input parameter uncertainty, and poor cross-year applicability of input-output carbon intensities, this study defines the accounting boundary using budget quotas and develops a hybrid life cycle assessment (HLCA) model. For easily traceable emission sources, process-based LCA (PLCA) is applied, with uncertainty analysis via distribution fitting and Monte Carlo simulation. For difficult-to-trace sources, input-output LCA (IO-LCA) is used with carbon intensity correction. A case study of a ±800 kV transmission line yields a construction-phase carbon emission intensity of 1,858.91 t·km⁻¹ (CO₂ equivalent), with a 95% confidence interval of [1,379.73, 2,486.45] t·km⁻¹. Sobol global sensitivity analysis identifies key emission reduction pathways. The method's validity is confirmed by comparison with existing studies, providing quantitative support for low-carbon design, construction optimization, and carbon auditing of UHV projects.