In terms of cost reduction and productivity improvement, the protection, automation and control systems of Portuguese Distribution Substations have experienced major developments during the last three decades. Those changes aimed to increase the quality of service, financial performance, flexibility, reliability and more capacity to monitor and control all the primary equipments of a substation. The trend of the Substation Automation System (SAS) is established using multifunctional Intelligent Electronic Devices (IEDs) and advanced communication technologies to provide a more effective locally and remotely substation monitoring and control.