by DeJim Lowe, Josh Shultz, Ian Grant, Tennessee Valley Authority; and Frank Lambert, Georgia Tech/NEETRAC
Tennessee Valley Authority (TVA) is a strong advocate of finding new and innovative ways to modernize the grid. Through the Smart Wire Focused Initiative (SWFI), sponsored by the National Electric Energy Testing, Research and Applications Center (NEETRAC), TVA has teamed up with the U.S. Department of Energy’s (DOE’s) Advanced Research Projects Agency–Electric (ARPA-E) and Smart Wire Grid Inc. (SWG) to deploy an array of distributed series reactance (DSR) units. The system is designed to provide congestion relief by redistributing power flow, thereby improving transmission system operations. The goal of this test bed is to prove this new technology can address flow-control issues in a cost-effective manner and be deployed with little, if any, outage time.
The hardware consists of an array of DSRs that easily clamp onto a transmission conductor. TVA has installed 99 DSRs (33 per phase, covering 17 tower spans) on a 161-kV transmission line near Knoxville, Tennessee, U.S. The DSRs allow operators to manage the current flow on the line by injecting inductive reactance on command, and they can be programmed to operate autonomously or with full operator control and provide distributed line sensing and monitoring. The distribution of the devices allows operators to vary the line impedance according to system needs. By using large numbers of low-cost, mass-produced devices, each array becomes immune to individual device failures.
TVA is leading a demonstration, supported by funding from NEETRAC’s SWFI members — TVA, Southern Company, Baltimore Gas & Electric and the National Rural Electric Cooperative Association — the DOE’s ARPA-E and the utility’s own energy delivery organization. This project represents a milestone in moving the smart wire technology from concept to development and into utility operations. The concept was created in 2005 by Dr. Deepak Divan, who is now at Georgia Tech. In 2006, the California Energy Commission provided basic lab development funding to Georgia Tech. Smart Wire was identified as a key enabling smart- grid-control technology in the DOE’s Modern Grid Initiative 2007 report.