Enhancing power system automation through the use of real-time ethernet

Since its inception in the early seventies, Ethernet technology has experienced wide acceptance and has exhibited exponential growth. It was only recently that Ethernet managed to virtually displace competing process bus and local area network (LAN) technologies-Token Ring, Profibus, Modbus (R) Plus, LonWorks (R), etc.-most of which had to switch to the Ethernet-based physical layer and TCP/IP-based protocols (Modbus TCP/IP, Profibus TCP/IP, and DNP TCP/IP). Ethernet is still widely believed to be inadequate for mission-critical, hard real-time applications because of inherent limitations associated with the traditional collision-based access techniques. However, fostered by the development of international standards (IEEE 802.3x, 802.1 q, 802.1p, 802.1w, IEC 61850-x-x), Ethernet has now evolved into a highly predictable and reliable real-time network technology. This paper provides an overview of the latest standards and investigates their impact on power system automation and protection. We give special attention to the use of the IEC GOOSE and IEC GSSE messages and to new options for streaming analog data over Ethernet described in IEC 61850-9-2. The paper includes application examples describing use of real-time Ethernet in distribution substation and industrial plant automation, such as fast bus trip, permissive transfer trip, and network reconfiguration-based breaker failure protection.