Case study: Application of wide-area, communications-assisted remedial action schemes improves transmission reliability

At Southern California Edison (SCE), remedial action schemes (RASs) are implemented to ensure reliable power system performance following outages on a transmission grid network. They include fast, automatic telecontrol actions (wide-area teleprotection) to mitigate thermal overloads and system instability upon the loss of one or more transmission lines. These communications-assisted RAS systems are intended to be used throughout the SCE area of operation, as well as at all interties to neighboring utilities to facilitate dynamic load shedding, generation tripping, and improved load management. With appropriately fast and deterministic communications, RAS systems are used in place of expensive alternative measures, which include reconductoring transmission lines, building new lines, and/or adding new transformers. Testing six years ago at SCE demonstrated the successful use of IEC 61850 Generic Object-Oriented Substation Event (GOOSE) messages over a distance up to 460 miles to collect analysis and arming data and transfer status and telecontrol. Devices designed to carefully manage teleprotection and GOOSE telecommunications are unaffected by the additional traffic of in-service installations with multiple devices networked together. However, subsequent research has shown that shared bandwidth Ethernet with typical substation traffic degrades the performance of GOOSE telecontrol within poorly designed IEDs from milliseconds to minutes. This paper focuses on the negative impact of Ethernet and Internet Protocol (IP) methods on mission-critical applications, why they are not widely recognized, and how to mitigate them. Research results and best practice recommendations of using Ethernet and time-division multiplexing (TDM) methods for telecontrol to solve transmission corridor stability issues are presented.