In 1999, ComEd (Chicago, Illinois, U.S.) and Southwire (Carrollton, Georgia, U.S.) began investigating a new concept to accurately determine the thermal behavior of overhead transmission lines during operation. The conductor temperature dictates the thermal rating and available clearance under a line. However, as of yet, no one has developed a satisfactory method to measure con-ductor temperature axially throughout its length as well as radially.

ComEd and Southwire's Fiber-Optic Transmission Conductor (FOTC) provides the medium for utilities to determine the real-time thermal operating limit of a transmission conductor in the most accurate way possible, as well as the means to transmit data or voice communications.

Operational on ComEd's system since Feb. 21, 2002, the 138-kV FOTC system uses distributed temperature sensing (DTS) to measure the temperature of the optical fibers embedded in the conductor. DTS allows accurate temperature measurement along the entire length of the FOTC line at different locations within the conductor.

The installation method was the same as a conventional one, except ComEd took special care to separate and protect the optical fibers from the conductor at the deadend location. Prior to the field demonstration, the FOTC system was tested and characterized by the National Energy, Testing, Research and Applications Center (NEETRAC) and Oak Ridge National laboratory.
Circle 177 on Reader Service Card or visit freeproductinfo.net/tdw