This paper addresses the requirements for loop closing operation under different voltage levels and distribution methods, and proposes a complete design method for loop closing devices. Firstly, based on the access conditions across voltage levels/distribution methods, the topological structure of the loop closing device was systematically designed and lightweight optimization was carried out; Secondly, a complete design process for phase-shifting transformers was established, and detailed calculation methods for key parameters were provided; Finally, through a combination of circuit inductance calculation and simulation verification, a comprehensive analysis was conducted on the correctness and feasibility of the design scheme. The research results show that this design scheme can effectively meet the technical requirements for loop closing operation.