Abstract: As the starting point of substation design, the main connection design determines the connection methods between various electrical equipment inside the substation, providing clear guidance for subsequent equipment selection, layout, and protection configuration. This article studies the data structure, design and drawing ideas, and fast drawing of the main connection. By designing a hierarchical drawing data and adopting the "top-down" design drawing concept, combining modular node splicing and historical data reuse technology, achieve rapid drawing of the main connection of traction substations.