Objective A large number of design follow-ups and actual operation data show that there is a significant deviation between the required capacity and the design capacity of metro main transformers, and a low load rate operation phenomenon of the main transformer is usually existing. The capacity calculation of main transformers involves complex load composition and statistical methods, with numerous complex influencing factors and high calculation difficulty. However, the determination of the capacity value directly relates to the construction investment scale of the main substation. Therefore, it is necessary to conduct a targeted research to optimize the calculation accuracy.

Method The metro power supply system architecture and the crucial functions of the main transformer within the system are briefly elaborated. The influencing factors on the capacity of metro main transformers are analyzed, and the existing problems in the power supply system design are clarified. Taking the metro network in a southern China city as a research case, the network operational data from 2016 to 2023 are selected, and an energy consumption index method based on actual engineering and operation data is proposed to optimize the metro main transformer capacity calculation method. The applicability of this algorithm is also verified.

Result & Conclusion  The predicted value of the main transformer load rate based on the energy consumption index method is quite consistent with the actual value, primarily manifesting as a certain positive deviation. From the perspective of reliability and redundancy, the main transformer capacity prediction results based on the energy consumption index method can meet the engineering design accuracy requirements.