Guadalupe Valley Electric Cooperative (GVEC) in south-central Texas has become the nation’s first rural electric cooperative to install 3M Aluminum Conductor Composite Reinforced (3M ACCR) electrical-transmission cable, an advanced overhead transmission conductor for grid applications, developed by 3M (St. Paul, Minn.). GVEC’s Feb. 8 announcement noted that the 2.8-mile/4.5-km, single-circuit 138 kV line provides power for the city of Schertz, situated about 20 miles/32.2 km northeast of downtown San Antonio. 3M’s high-capacity ACCR conductor replaces a conventional steel-cored ACSR conductor on this line.

The utility deployed the lightweight, low-sag, high-capacity cable on a transmission line that links two substations. Use of the cable enabled GVEC to increase the line’s capacity by more than 60 percent without enlarging towers or widening the right of way. Rene Hernandez, a GVEC system engineer, says the new conductor was chosen after an extensive review of the transmission load issues and the economics regarding replacement and addition of steel transmission structures: “The higher-ampacity conductor afforded GVEC the additional capacity needed to meet the planning requirement, at a substantial savings to the GVEC membership.”

3M ACCR is now in use by major utilities and municipal power companies throughout the U.S. and in Europe, Asia and South America. Introduced for commercial use in 2005, 3M’s innovative metal-matrix composite conductor was developed with the support of the U.S. Department of Energy, which tested the conductor at its Oak Ridge National Laboratory (ORNL) in Tennessee, and with early contributions by the Defense Advanced Research Projects Agency (DARPA). The conductor’s strength and durability result from its metal-matrix composite core, composed of aluminum oxide (alumina) fibers embedded in high-purity aluminum. It has the durability and longevity of traditional steel-cored conductors and better thermal performance, which reduces line sag. According to 3M, all U.S. and international ACCR installations, some in place for more than a decade, have operated successfully, thus far, with no failures.