Southwestern recently completed an upgrade project for the Dardanelle-Clarksville transmission line in Arkansas. The rebuilding of nearly 35 miles of 161kV transmission line improves Southwestern’s continued ability to provide reliable and cost-efficient electric power to its customers.
Southwestern Power Administration
August 12, 2025
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Southwestern Power Administration (Southwestern or SWPA) recently completed a two-part upgrade project for the Dardanelle-Clarksville transmission line in Arkansas. The rebuilding of nearly 35 miles of 161kV transmission line improves Southwestern’s continued ability to provide reliable and cost-efficient electric power to its customers, supporting Southwestern’s mission and regional transmission needs.
The upgrade was split into two construction projects. The first project included rebuilding predominantly H-frame transmission line from Clarksville to Structure 87 and was completed in May 2022. The second project included reconductoring the double-circuit lattice steel tower transmission line from Dardanelle to Structure 87, which was completed in July 2025.
Southwestern resolved several design challenges during this project, including the large cost and significant time it would take to replace the existing steel lattice structures if traditional Aluminum Conductor Steel Reinforced (ACSR) conductor was used. Through research and careful planning, Southwestern determined that an advanced conductor was needed for the project and was able to identify a lightweight conductor that the Western Area Power Administration (WAPA) had already deployed with excellent operational and reliability performance, which resulted in significant time and cost savings for the project. The original ACSR conductor was replaced with an Aluminum Conductor Composite Reinforced (ACCR) advanced conductor. In addition, Optical Ground Wire (OPGW) was installed above each transmission circuit. The new ACCR transmission line conductor incorporates high-strength, lightweight materials, which increased the line rating by almost 60 percent.
“The successful completion of this critical project stands as a testament to the dedication, coordination, and technical expertise of all Southwestern personnel across multiple divisions, each of whom played a vital role in achieving this milestone,” Southwestern Administrator Marshall Boyken said.
Getting Technical
The new ACCR transmission line conductor incorporates a high-strength, lightweight aluminum matrix core wrapped with one or more layers of current-carrying strands composed of a hardened aluminum-zirconium alloy. The aluminum matrix core, which provides most of the structural strength, as well as the aluminum-zirconium alloy strands, are capable of operating at high temperatures and have a low thermal coefficient of expansion. This enables the conductor to achieve higher ampacity than traditional ACSR conductors. These properties not only enhance strand durability but also contribute to the overall strength of the conductor.