Dive Brief:

• A proposed 300 MW direct current interconnection between the electric grids in southern Arizona and the northwest region of Mexico could be operational in 2019, according to Arizona Public Media.
• The Nogales Interconnection Project is being developed by Hunt Power and Unisource Energy, the sister company of Tucson Electric. It would allow for power sales between the U.S. and Mexico, as well as emergency power supplies in case of reliability issues.
• Plans call for a three-mile, 138-kV transmission line originating at UniSource Energy Services Valencia Substation in Nogales, extending west and south to the new Gateway Substation, and a two-mile 230-kV segment extending south from Gateway into Mexico.

Dive Insight:

Arizona Public Media reports Hunt and Unisource are continuing work on the Nogales Interconnection, which was first proposed in 2015. Officials told the media source that the development of the project is a result of Mexican President Enrique Peña Nieto's work to open his country's power markets.

According to Hunt's description of the project, the Nogales tie will boost electric reliability, "including providing bi-directional power flow and voltage support as well as emergency assistance, as needed, for the electric system both north and south of the border."

Nogales is at the end of the Western Electricity Coordinating Council grid, and according to Hunt the city relies on a 55-mile, 138-kV line for its power supply. Adding the Gateway Substation and transmission tie to Sonora, Mexico, will provide emergency backup on both ends of the line.

The project's DC interconnection is necessary because the Arizona and Sonoran grids are not in phase, which means a synchronous interconnection is not possible.

Hunt's description of the project explains that the DC interconnection "will provide greater stability and reliability to both the Arizona and Sonora grids by allowing one grid to be a back-up source of power to the other in time of peak demand."