Each particular Substation Automation System (SAS) will have a lot of attributes imposed by different factors such as user requirements, provider philosophy, hardware/software capabilities and the state‐of‐the‐art in technology when they are implemented. This chapter gives an overview of several of them intending to provide guidelines for engineers dealing with SASs in different project stages. Modern SASs are designed using a decentralized automation concept based on a hierarchical structure conformed by the control levels including remote control level, station level, bay level and process level. Such a concept is characterized by the intensive use of Intelligent Electronic Devices (IEDs) and the implementation of optical fiber links for data communication between IEDs. Appropriate network topology should be defined for each specific SAS project based on the required data handling, quality requirements according to the operative significance of the substation, commissioning requirements during the installation of the SAS and cost impact.