Life cycle CO2 emissions of various transformers under different scenarios with multiple functional units

Despite extensive research on transformer life cycle carbon emissions, the selection of an appropriate functional unit remains challenging. Many commonly used functional units inadequately reflect transformer functionalities, hindering accurate comparisons across different voltage levels and capacities. This study performs a life cycle carbon emission analysis to evaluate the impact of different functional unit settings on ten transformers. The average emission per studied transformer is 223.47 t CO₂eq. Carbon emission varies remarkably based on the choice of the functional unit, with values of 6955.40 kg CO₂eq/MVA, 9.83 kg CO₂eq/(MVA kV), 81.08 kg CO₂eq/(kW h) and 1.36 × 10⁻⁴ kg CO₂eq/(MW h kV). Metals are identified as the primary contributors to the overall carbon footprint of transformers, accounting for approximately 73.91% of total emissions, with steel contributing up to 42.98%. Selecting greener raw materials, employing recycled materials and using clean energy in production can help reduce transformer carbon emissions. Scenario analysis reveals that improvements in the electricity generation mix reduce emissions during transformer production by 9%–11%, depending on the level of improvement, with larger improvements demonstrating greater reduction rates. The findings of this study provide insights for selecting appropriate functional units for the carbon assessments of transformers and offer a reference for formulating targeted emission reduction strategies to support the power sector's low-carbon transition.