3M aluminum composite expands application in power

To avoid tower construction on the banks of the Chehalis River in an environmentally sensitive area near the river's mouth, Grays Harbor Public Utility District will become the first electric utility in Washington State to deploy the new 3M Aluminum Conductor Composite Reinforced.

To avoid tower construction on the banks of the Chehalis River in an environmentally sensitive area near the river's mouth, Grays Harbor Public Utility District will become the first electric utility in Washington State (USA) to deploy the new 3M Aluminum Conductor Composite Reinforced (3M ACCR, St. Paul, Minn., USA) this summer, as part of a general upgrade of its transmission lines.

The light-weight, low-sag conductor provides higher transmission capacity without requiring larger towers or rights of way. It will be applied on a 1,676-ft/511m span of three lines as they cross the river near Aberdeen, in Grays Harbor County. Installation of two 115-kV circuits and one 69-kV circuit is scheduled to begin in late July, replacing copper conductors.

The low-sag characteristic of 3M ACCR also will create greater clearance between the transmission lines and fiber optic cable running just beneath them.

The Chehalis flows northward out of the mountains of southern Washington, picking up several tributaries along the way, and then turns westward through Grays Harbor County. The river becomes an estuary as it encounters tidal influences — intensifying its environmental importance — while approaching Grays Harbor Bay and the Pacific Ocean at Aberdeen.

"It is a significant advantage to be able to upgrade three circuits on the same crossing, together with the under-built fiber optics, without having to enlarge the towers," says Phil Penttila, system engineering supervisor for Grays Harbor PUD. "This allows us to avoid the permitting and other potential delays that we are likely to have faced with a construction project along the river."

3M ACCR, which had its first commercial application in 2004, is now in use by dozens of utilities of all sizes and types in the U.S. and six other countries, including other municipal utilities in California and Colorado. The conductor is most often used for line upgrades in areas where new construction or expanded rights of way would cause environmental disturbance or pose difficult social and logistical issues, in both rural settings and dense urban areas.

The conductor's strength and durability result from its core, composed of aluminum oxide (alumina) fibers embedded in high-purity aluminum through a highly specialized and patented process. The constituent materials can withstand high temperatures without appreciable loss in strength, even over long periods of time.