Carbon Emission Accounting Method for Ultra-High Voltage Transmission Line Construction Considering Carbon Intensity and Activity Data Uncertainty

• • The HLCA model quantifies construction-phase carbon intensity of a ±800 kV UHV line as 1,858.91 t·km⁻¹ (CO₂ eq), with a 95% confidence interval of [1,379.73, 2,486.45] t·km⁻¹, enabling probabilistic rather than point-value assessments for regulatory compliance and carbon trading. • • Material production dominates emissions, accounting for 86.13% of total construction emissions, while construction activities contribute only 3.53% and other expenses 10.35%, highlighting that supply-chain interventions yield the highest decarbonization leverage. • • Sobol global sensitivity analysis identifies conductor carbon emission factor and conductor input quantity as the most critical parameters, meaning that precise data collection and low-carbon conductor procurement are essential to reduce uncertainty and improve accounting accuracy. • • The model integrates PLCA with Monte Carlo simulation (using lognormal distributions) and IO-LCA with temporal correction for purchasing power and carbon intensity, addressing cross-year applicability gaps and reducing systematic errors in long-duration infrastructure projects.