3.1.1. IEC 61850

IEC 61850 is an international standard of communication networks and systems for power utility automation. This standard in the 2003 edition focused on the automation of power system substations

and was divided into three levels: Process, Bay, and Station. In the process level, measurement equipment such as current transformers (CT), potential transformers (PT), or phasor measurement units (PMU) are located and send measurement data to the bay level, which is the place of intelligent electronic devices (IED) issuing control and protection commands based on the received information. The process level communicates with one or more bays, and even the whole substation, as well as exchanging information with the engineering workplace for remote control commands. All of this information exchange in a form of three types of the message, including manufacturing message specification (MMS) for non-critical information and in the format of request-response, generic object-oriented substation event (GOOSE) for critical information with high priorities such as trip command and sampled value (SV) for measurement units with high priority. GOOSE and SV are of multicast format. Each of these messages has its time limitation and is mapped according to the communication stack proposed in part 8–1 of the standard, which uses an open system interconnection (OSI) model and Ethernet as a physical layer in the LAN environment. In MG, an IED is located in each DER for the control and protection of objects. The nature of MG is that it is positioned in remote places desiring interconnection with the main grid through WAN. An extension of IEC 61850 in successive editions by information model supporting MG in part 7–420, 90—7, and providing a communication stack for interconnection in WAN based on applying eXtensible Messaging and Presence Protocol (XMPP) for mapping information in part 8–2 makes this standard appropriate for use in the MG communication environment. However, it is noted that other IoT protocols are suggested in other literature, and laboratory experiences perform better than XMPP in comparison with QoS, implementation infrastructure requirements, and future development specifications [41,42].
