Comprehensive evaluation of low-carbon construction in ultra-high voltage projects based on life cycle and matter-element extension theory

Ultra-high voltage (UHV) projects serve as critical infrastructure for large-scale clean energy transmission in China and represent a core strategy for advancing the country's low-carbon energy transition. To comprehensively assess the low-carbon performance of UHV project construction, this study develops an evaluation system based on the energy-economy-environment (3E) coupling theory and life cycle theory. The index weighting is determined using the AHP-DEMATEL method, and a rigorous evaluation is conducted using the matter-element extension model. This methodology is applied to evaluate both the construction process and the low-carbon improvement plan of a newly built 1000 kV substation project in Southwest China. The study highlights the importance of the design and recycling phases as integral components of low-carbon evaluation for UHV projects. Furthermore, the evaluation results confirm that embodied carbon in the procurement stage and operational carbon reduction achieved through the design phase are critical factors that warrant close attention. The proposed evaluation method demonstrates extensive applicability. • A full life-cycle framework evaluates low-carbon performance of UHV projects. • AHP–DEMATEL identifies causal and influential low-carbon indicators. • A matter-element extension model enables multi-level carbon assessment. • Real 1000 kV substation data validate the evaluation approach. • Low-carbon technologies greatly enhance energy and environmental outcomes.