Celanese Corp. and U.S. wire and cable maker Southwire Co. LLC have developed an overhead transmission line made of thermoplastic composites to replace traditional wires that use aluminum as conductors and are reinforced with steel.

The transmission line, called C-7, uses a composite core of bundled strands made of Celstran long-glass fiber-reinforced thermoplastic combined with heat-resistant Fortron polyphenylene sulfide and is covered with a layer of PEEK (polyetheretherketone).

The cable harness is housed in a sheath made of aluminum or aluminum-zirconium alloy.

Celanese and Southwire Corp. introduced the lightweight composite wire earlier this year after seven years of development. Celanese demonstrated the application at the JEC Americas Composites Show in Atlanta in May.

Benefits include reduced increase in sag at high power transmission, thanks to reduced thermal expansion. The stranded core design means there is no single point of failure, as can occur with monolithic cables.

Southwire, based in Carrolton, Ga., says composite wires have a service life of more than 40 years.