Abstract: As an important part of the secondary circuit of the conventional substation, the substation terminal plays the role of connecting and disconnecting the secondary circuit. In recent years, due to the lack of space in the panel cabinet, it is difficult to implement the rectification of the South China Power Grid Countermeasures of "crimping two wires at the same terminal", and there have been many accidents of expanding the scope of power outage due to unreliable circuit connection. Through research, this research group has carried out the research on the transformation method of power secondary equipment without power failure and the live expander of general-purpose substation terminal interface. After long-term field use verification, it can live and reliably expand the terminal interface, making the transformation method of "parallel connection first and then demolition" more applicable. This achievement can overcome the long-standing problems on the site, such as the full arrangement of terminal strips and the difficulty of power outage transformation. It plays a significant role in the rigid implementation of Countermeasures in the southern power grid, the transformation of circuits without power outage, the reduction of power grid operation risk and the improvement of power supply reliability.