Digital substation concept improves substations in advance by enhancing the equipment at station level, bay level, and process level. This enhancement of substation requires changes of equipment at those levels. The design needs to meet each equipment’s compatibility with the others. However, some manufacturers of the digital substation in Indonesia provide different specifications for the equipment at the same level. This condition causes challenges of implementation design of the digital substation in existing substations. To enhance existing substations including conventional substation and modern substation, the digital substation specification and equipment are reviewed. The reviews are based on digital substation standards including communication protocol, network redundancy, and time synchronization. After the specification study, the provided equipment in Indonesia are compared based on their technical specification. The technical specifications are compared at station level, bay level and process level based on provided equipment in Indonesia. The compatibility study is analyzed by using provided equipment, following with the implementation study in Indonesia. This paper provides reviews of the technical specification gap of existing substations compared to the digital substation. Finally, the consideration of choosing technical specifications also provided when implementing the digital substation in Indonesia.