In the late 80's the Oncor Electric Delivery transmission planners identified a need for a 345 kV source into the center of the Dallas metropolitan area. This source would require the installation of a 345 kV transmission line, and establishment of a 345/138 kV switchyard to strengthen the 138 kV power grid and meet the needs for future growth. In March 1991, the Watermill - West Levee 345 kV line construction was completed and the line energized. The line was designed utilizing double circuit steel poles, and vee string insulator assemblies, with 2-1590 kcmil conductors per phase with only one circuit initially installed. It was anticipated that the second circuit would not be required for at least 10 years. At this point in history, the prospect of joint use of right-of-way was being pursued as a viable solution to routing issues by regulatory agencies. Approximately nine miles of the transmission line was built on a single-track Union Pacific railroad ROW with nominally 25 ft separation from pole center to the center of the track. However, when the line was energized the railroad signal equipment began to malfunction. Measurements showed that an induced 60 Hz rail-to-ground track voltage condition in excess of 65 volts at one location. There were also values as high as 115 volts measured across some of the insulated rail joints. Therefore, the line was temporarily removed from service until suitable mitigation measures could be developed.
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