Evaluation Method for DC Bias Impact on Power Grid Considering Metro Stray Current Growth

This paper proposes a comprehensive evaluation method to quantify the impact of the increasingly networked metro system on the power grid. The method specifically evaluates the DC bias effect on transformers that considers the increase in stray current as the metro system grows. The goal is to provide theoretical support for maintaining grid stability. The paper also analyzes the DC bias mechanism and stray current intrusion paths.Based on this, an evaluation indicator system is developed. The system focuses on transformers, transmission lines, and cable armoring. And the FAHP-improved CRITIC method is used to assign weights to the indicators. This allows for a more comprehensive evaluation. A case study of a southern city's power grid is included. The case study demonstrates the method's application. It provides guidance on preventing DC bias. It also helps identify operational risks in transformers. Ultimately, it supports the stable operation of urban substations.