T&D World Magazine

Sahuarita-Nogales Transmission Line Project Proposal

Tucson Electric Power (TEP) is working with the Arizona Corporation Commission (ACC) and federal agencies to improve electric reliability for Santa Cruz County residents served by TEP's sister company, UniSource Energy Services (UES) by proposing a new 345-kV transmission line.

UES relies on a single 115-kV transmission line to feed a local distribution grid that serves more than 21,000 customers in Santa Cruz County. When that line fails, county residents can be subject to potentially lengthy power outages until the line is restored to service. UES has taken significant steps to reduce the length of such outages, including the installation of a new gas turbine generator in Nogales and construction of an emergency backup link to TEP's system. Nevertheless, a second transmission line would allow UES to maintain continuous service under such circumstances while meeting Santa Cruz County's future power needs.

To address this situation, TEP and UES have proposed building a new 345-kV transmission line from TEP's South Substation in Sahuarita to a proposed UES substation near Nogales, Arizona. TEP also hopes to extend the new line into Mexico, enabling international energy exchanges while improving electric reliability on both sides of the border.

The ACC authorized construction of such a line along the so-called Western Route in January 2002, but TEP and UES have not secured necessary federal permits for the project. Although federal agencies have not formally ruled on the proposal, a U.S. Forest Service official has said that agency would likely oppose construction along a portion of the ACC-route that passes through the Coronado National Forest.

In light of that conflict, the ACC has invited the U.S. Forest Service and other federal agencies to participate in a new review of the project, its proposed route and potential alternatives. That review is ongoing. Meanwhile, TEP filed a request on Feb. 2, 2006, for a new federal review of the project under the Energy Policy Act of 2005, which sets a one-year deadline for such studies.

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