Life-Cycle Based Carbon Footprint Assessment and Evaluation of Reduction Measures for AIS and GIS Substations

Previous life-cycle assessment (LCA) studies on substations have primarily focused on individual equipment, such as transformers and gas-insulated switchgear (GIS), identifying power losses and SF₆ leakage as major environmental emission sources (hotspots). However, for practical investment and renewal planning, it is essential to evaluate substations as integrated systems consisting of multiple pieces of equipment over their entire life cycle and to identify feasible emission reduction measures. Accordingly, this study aims to conduct a substation-level LCA beyond equipment-level assessments, and to identify hotspots as well as effective greenhouse gas (GHG) reduction measures across different substation types.

Two representative models were analysed: a 275 kV gas-insulated substation (275 kV-GIS) and a 77 kV air-insulated substation (77 kV-AIS). The assessment adopted a cradle-to-grave system boundary, covering all stages from raw-material procurement to disposal. The evaluation combined actual procurement records, construction specifications, manufacturer data, and a national life-cycle inventory (LCI) database to quantify life-cycle equivalent CO₂ emissions

(LC-CO₂eq). Power loss emissions were excluded, as they are highly dependent on the power generation mix and are beyond the control of utilities. The results showed that the dominant contributors (hotspots) to LC-CO₂eq were raw-material procurement and SF₆ leakage during manufacturing, operation, and disposal, while the impacts from transportation, installation, and non-SF₆-related maintenance were limited. Based on these findings, this study also conducted a systematic evaluation of the effectiveness of major emission reduction measures. In the 275 kV-GIS model, replacing SF₆ with a natural-origin gas achieved an overall emission reduction of approximately 26%, despite a modest increase in material-related emissions due to larger enclosures. In the 77 kV-AIS model, an overall reduction of around 60% was achieved by combining multiple reduction measures, including extending transformer service life, applying SF₆ alternatives, and adopting low-carbon materials. These results indicate that pursuing a combination of approaches—such as material substitution and equipment life extension—can maximize the overall emission reduction potential.

Overall, the findings indicate that hotspot-based substation-level LCA can support utilities in identifying and prioritizing effective decarbonization measures while accounting for differences in substation configuration and voltage level, thereby contributing to informed investment and renewal planning toward the decarbonization of substation.