Carbon Emission Accounting Method for Ultra High Voltage Transmission Line Construction Based on Process-Based Life Cycle Assessment

In the context of significant carbon emission pressures faced by China's power industry, there is an urgent need to establish a carbon emission accounting system suitable for the construction of ultra-high voltage (UHV) transmission lines. This paper, based on the life cycle assessment method and carbon emission factor method, clarifies the carbon emission accounting boundaries for the construction of UHV overhead transmission lines, formulates relevant selection criteria for carbon emission factors, and proposes a carbon emission calculation model to quantify emissions from materials production, transportation, and construction phases. To validate the proposed model, the differences in carbon emissions for multiple segments of 1000 kV and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm 800 \text{kV}$</tex> double-circuit overhead transmission lines across various terrains and different construction phases were analyzed. The findings reveal that during the construction of transmission projects, the carbon emissions generated from machinery and materials production stages account for the largest proportion, with higher per-unit-length carbon emissions observed in complex terrains, especially in mountainous areas. Furthermore, the carbon emissions per unit length of 1000 kV AC transmission lines are higher than those of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm 800 \text{kV}$</tex> DC transmission lines, primarily due to the former requiring more materials inputs. An effective tool for estimating carbon emissions in the construction of UHV transmission projects is provided in this study, promoting the green and low-carbon development of the power grid.