General Cable, Highland Heights, Ky., last month introduced an addition to its BICC brand bare overhead conductor line called TransPowr TW. Engineering Director Dennis Doss III says the Aluminum Conductor Steel-Supported/Trapezoidal Wire (ACSS/TW) de sign's fully annealed "O"-temper aluminum "causes most or all of the mechanical load to be transferred to the steel core," allowing the conductor to "operate continuously at more than twice the accepted temperature limit of [conventional aluminum conductor steel-reinforced–ACSR] with significantly less sag." Higher temperature means the conductor can carry more current.

EFFICIENT New conductors, more current (Photo courtesy of General Cable)

The Dept. of Energy and 3M Corp., St. Paul, Minn., are testing a conductor design that uses a core of aluminum-matrix-composite wires surrounded by temperature-resistant aluminum-zirconium wires. 3M calls it Aluminum Conductor Composite-Reinforced, or ACCR.

The composite core is "stronger than steel, and it doesn't elongate like steel," says Philip Overholt, DOE transmission reliability program manager. 3M claims the ACCR can carry 11�2 to 3 times as much current as ACSR of the same size.

The Tennessee Valley Authority has strung a test line near Oak Ridge with what Overholt calls "small conductor"–477 kcmil. Researchers will test it with high currents in some 500 cycles by the end of the year to determine how it performs, he says.

The Western Area Power Administration also will test a mile-long, 230-kv installation near Fargo, N.D., under some of the most challenging weather conditions in the U.S. Overholt says this "medium-size conductor"–795 kcmil, will undergo six months of testing.

ew conductor designs now being tested could lead to expansion of the current-carrying capacity of existing electric-transmission systems without extensive construction of new lines. The designs increase the capacity as much as three times, while reducing the tendency of overheated lines to sag, their designers claim.