Abstract: Based on the on-site practice and taking a 220 kV line protection replacement project as an example, the wiring forms of public voltage circuits in the secondary system of the substation are sorted out,descriptions on the public voltage disconnecting and connecting scheme for the project are made, and the principles of formulating the scheme, typical risks, and preventive measures are summarized, which offers reference for on-site personnel to safely and efficiently complete the disconnecting and connecting activities.