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Power
New Conductor Designs Tested
(enr.construction.com
- 9/02/02 issue)
By Thomas F. Armistead
New 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.
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.
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| EFFICIENT New conductors, more current (Photo courtesy of
General Cable)
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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 11Ú2 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.
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