Wilson Dam & Hydroelectric Plant, Oilostatic Transmission System, Spanning Tennessee River at Wilson Dam Road (Route 133), Muscle Shoals, Colbert County, AL

Significance: As generating capacity at Wilson Dam grew through the early TVA years, new methods of generator cable installation came into practice. One of these new cable installations, the Oilostatic System, was introduced to Wilson Dam in 1943. Using oil-filled pipe pressurized to 200 pounds per square inch, two generator main connections of approximately 1,435 and 1,780 feet in length were installed in conjunction with generator units 15 and 16 of the dam's 19-unit-capacity powerhouse. In 1947, units 13, 14, 17 and 18 were installed with the new system. At the time of Wilson's first cable installation in 1925, common practice was to wrap generator leads in impregnated paper and then cover them with a lead sheath. Wilson's first leads were simply wrapped in braided cotton. However, when increased loadings were found to be limited by high dielectric losses in the cable, and when subsequent insulating materials developed problems with ionization, the Okonite-Callender Cable Copmpany developed its Oilostatic Transmission System, unveiling its first commercial design in 1932. In addition to handling increased loadings, the Oilostatic system was installed at Wilson in order to fit the limited space available, to conserve copper, and to provide good protection against mechanical injury. The oilostatic system included a twin pumping plant for pressurizing the oil within the cable while maintaining the oil under a vacuum to prevent oxidation. Specially designed terminating joints and bushings would keep cable connections within pressurized oil, allowing the transfer of current to substations and switchyards.
Unprocessed Field note material exists for this structure: N166
Survey number: HAER AL-47-B
National Register of Historic Places NRIS Number: 66000147