The desire to provide highly available power with reduced staff drives utilities and system owners to automate substations. This chapter discusses the functionality and distinctions between the devices. Substation automation projects vary greatly when comparing a new substation and the upgrading of the equipment in an existing station. Interoperability of legacy devices and new automation devices is a real concern. The focus of the data communicated out of the substation has been for many years focused on operational data such as circuit breaker positions, volts, and amperes. Digital fault records, circuit breaker contact wear indications, dissolved gas, and moisture in oil are examples of nonoperational data. The configuration and settings for the intelligent electronic devices (IEDs) in the substation are at least as important as the operational and nonoperational data produced by fully functional IEDs. The integration of IEDs in a substation protection and control system is a technical issue.