To solve the problem of DC bias and bias effect of a transformer

a method for identifying the key substation stations that affect the DC bias current distribution of transformers is proposed. On the one hand

based on the system structure

the importance index of bias current connection is constructed to reflect the bias. The magnetic current circulation path plays a key role in the substation node. On the other hand

from the perspective of the system DC distribution

the concept of the node-node influence degree index is defined to measure the severity of the DC bias effect of the transformer on the system. Combined with the two aspects above

the propagation mechanism of bias current and the identification method of key sites are studied. The actual engineering case is used for analysis

and the feasibility of the method is verified. The research results may provide the theoretical basis and useful reference for DC bias treatment of substation for practical engineering.