Developers want transmission project to connect Arizona, Mexico power grids

transmission lines august 1 elp

Nogales Transmission, and UNS Electric, in an application with the Arizona Corporation Commission, requested from the Arizona Power Plant and Transmission Line Siting Committee certificates of environmental compatibility for authority to build two related transmission projects: the Nogales Interconnection Project and the UNSE Nogales Tap to Kantor Upgrade Project.

Together, those projects are referred to in the application as the CEC Transmission Facilities or the facilities, the companies said.

The facilities would result in an asynchronous connection between the electric grid in southern Arizona and the electric grid in northwestern Mexico, offering such benefits to each system as access to additional energy sources, markets, and ancillary services; cost savings; and economic development, the companies said.

The facilities would support the reliability of each electric system, including providing bidirectional power flow, voltage support, and emergency assistance, as needed, for the electric systems north and south of the international border, the companies said.

The Nogales, Ariz., area, which relies on a single transmission line for power supply, would obtain access to additional sources of electricity in the event of a reliability emergency, the companies said.

The Nogales Interconnection Project consists of these three components, all of which would be located in Santa Cruz County, the companies said:

·      A UNSE 138-kV Gateway substation and a Nogales Transmission 230-kV Gateway substation, which would be the location of high voltage direct current (HVDC) converter equipment, referred to collectively as the Gateway substation

·      A new nearly three-mile, double-circuit, 138-kV transmission line to be built by UNSE – one circuit to extend the existing UNSE Vail to Valencia line from a point near UNSE’s Valencia substation to the proposed Gateway substation, and one circuit to connect the new Gateway substation to the existing Valencia substation

·      A new nearly two-mile, single-circuit, 230-kV transmission line to be built by Nogales Transmission on double-circuit capable structures that would connect the proposed Gateway substation to the U.S.-Mexico border, where it would interconnect with the Red Nacional de Transmisión (RNT), the state-owned transmission grid operated by Centro Nacional de Control de Energía

The companies noted that entities on both sides of the international border have taken initial steps to facilitate the Nogales Interconnection Project, which is being jointly developed by MEH Equities Management Co. and Nogales Transmission, which is an indirect unit of Hunt Power, L.P., which is an indirect unit of Hunt Consolidated, Inc.

The Nogales Tap to Kantor Upgrade Project, to be built by UNSE on a 27.5-mile segment of UNSE’s existing 138-kV transmission line that serves Santa Cruz County, is necessary to provide the transmission capacity to support the Nogales Interconnection Project and strengthen the UNSE transmission system in the area, the companies said.

Upgrading the 27.5-mile segment between a point near the Western Area Power Administration (WAPA) Nogales Tap switchyard and UNSE’s Kantor substation would include replacement of the existing conductor and the existing steel monopoles, the companies said. Depending on the approved route, relocating some of the transmission infrastructure outside the existing alignment may be necessary, the companies noted.

UNSE, Tucson Electric Power, and MEH – an investment holding company – are subsidiaries of UNS Energy Corp., which is a unit of Fortis, the companies noted.

Nogales Interconnection Project

Further discussing the facilities, the companies noted that the proposed Gateway substation would be built on 11 acres of land that Nogales Transmission expects to acquire from TEP. About 1.8 acres of the substation site would be used to build the UNSE Gateway substation, which would serve as the new point of termination of the 138-kV transmission line currently extending from Vail to Valencia, and the point of origin of the proposed Gateway to Valencia 138-kV transmission line, the companies said.

The UNSE Gateway substation would also accommodate connections to the “Phase I and II” HVDC equipment and future UNSE distribution facilities, the companies said.

In Phase I of the Nogales Interconnection Project, the facilities would include a converter capacity of 150 MW, while a second phase of the project – the timing of which will be determined by market demand – would expand the converter capacity to 300 MW (Phase II), the companies said.

About nine acres of the substation site would be used to build the Nogales Gateway substation, where both the Phase I and II HVDC equipment would be located, the companies said, adding that the Nogales Gateway substation would serve as the point of origin of the proposed Gateway to U.S.-Mexico Border single-circuit 230-kV transmission line on double- or triple-circuit capable structures, depending on the route approved.

One circuit of the nearly three-mile, 138-kV, double-circuit transmission line would originate at an existing pole 1,900 feet west of UNSE’s existing Valencia substation, where the existing Vail to Valencia line would be severed and connected to one circuit of the new double-circuit line, the companies said. The circuit would proceed in a westerly direction to the proposed Gateway substation, thereby converting the existing Vail to Valencia transmission line to the new “Vail to Gateway” transmission line. Like the existing Vail to Valencia transmission line, the new line would be built on self-weathering tubular steel monopole structures ranging in height from 75 feet to 110 feet, the companies added.

The second circuit of the nearly three-mile line would originate at the proposed Gateway substation, and proceed in an easterly direction along the double-circuit structures supporting the new Vail to Gateway transmission line to a pole 1,900 feet west of the existing Valencia substation, where it would connect with the existing portion of the UNSE 138-kV line that travels east to the Valencia substation.

The companies added that that circuit would constitute the new “Gateway to Valencia” transmission line. The line would be built on self-weathering tubular steel monopole structures ranging in height from 75 feet to 110 feet, the companies said.

The nearly two-mile, 230-kV transmission line would originate at the proposed Gateway substation and extend south to the U.S.-Mexico border, interconnecting to a new transmission line in Sonora, Mexico, the companies said. It would be built on self-weathering tubular steel monopole structures roughly 95 feet to 115 feet in height.

Depending on the route selected, a short stretch of that line may include two parallel pole structures to accommodate a new single-circuit, 230-kV line and a new double-circuit, 138-kV line, a triple-circuit structure with a new single-circuit, 230-kV line, and a new double-circuit, 138-kV line, or a single-circuit, 230-kV line on double-circuit capable poles, the companies added.

Based on certain studies, as well as landowner and stakeholder feedback, the companies said that they selected the nearly 5.1-mile “Alternative Route 3” as the preferred route for the Nogales Interconnection Project. That route would begin at the existing Valencia substation and follow an existing UNSE transmission line corridor west for about 0.4 mile.

The route would use the existing conductor and poles for about 1,900 feet on an existing 138-kV UNSE line, the companies added, noting that the route would then continue, using double-circuit, 138-kV construction, south and then west, crossing I-19 and the Mariposa Wash. The route would continue southwest along a property line and on the north side of the Mariposa Wash to Mariposa Road, then cross Mariposa Road and continue along the south side of the Mariposa Wash for 0.6 mile. The companies added that the route would then head north for 0.75 mile to the proposed Gateway substation.

At the western end, both circuits would be connected to the Gateway substation, while at the eastern end, the existing Vail to Valencia line would be severed and connected to one circuit of that new line, thereby converting the existing Vail to Valencia line to the new Vail to Gateway transmission line. The companies added that the second circuit would connect with the existing portion of the UNSE 138-kV line at an existing pole 1,900 feet west of the existing Valencia substation, and travel east along the north side of W. White Park Drive to the Valencia substation. That circuit would constitute the new Gateway to Valencia transmission line.

The companies added that the Gateway to U.S.-Mexico Border 230-kV line portion of Alternative Route 3 would originate at the Gateway substation and follow the same path out of the Gateway substation as the 138-kV line for 0.6 mile. The route would continue southwest on the north side of the Mariposa Wash and then continue south to the international border, where the 230-kV line would connect to a line to be built in Mexico, the companies added.

The estimated subtotal cost of Alternative Route 3 is $80.2 million; that is, $7.2 million for transmission construction and $73 million for substation construction – the ROW acquisition cost is “TBD,” the companies noted.

Nogales Tap to Kantor Upgrade Project

Of the Nogales Tap to Kantor Upgrade Project, the companies noted that based on a system impact study conducted by UNSE that was completed in July, upgrades to a portion of UNSE’s existing Vail to Valencia transmission line between a point near the Nogales Tap to the Kantor substation are necessary to support the Nogales Interconnection Project.

That nearly 27.5-mile segment was not upgraded in 2013 with the remainder of the Vail to Valencia line, and therefore lacks sufficient capacity to support the project, the companies said. The upgrade requires replacing the existing Darien 559 AAC conductor with Rail 954 ACSS-HS conductor, which necessitates replacement of the existing steel monopoles, the companies said.

The Nogales Tap to Kantor Upgrade Project would be rebuilt on self-weathering tubular steel monopole structures ranging in height from 75 feet to 110 feet, the companies said.

Depending on the route approved, the work on the upgrade segment would involve replacing the conductor and poles in the existing ROW, where possible, and relocating poles within new or amended ROWs on private or state land, the companies noted.

After gathering feedback from landowners, the companies said that they selected the nearly 27.5-mile “Alternative Route 1” as the preferred route for the Nogales Tap to Kantor Upgrade Project.

That route begins 320 feet south of the Nogales Tap on the west side of Wilmot Road at existing pole no. VL-KA-5-2, and continues 9.5 miles south along the west side of Wilmot Road, in an entirely new ROW, to a point where the existing transmission line corridor turns southwest, and continues diagonally for 18 miles to the Kantor substation.

The companies added that the diagonal section would be offset from the existing ROW 30 feet to the west from the end of Wilmot Road to Mt. Hopkins Road and 30 feet to the east south of Mt. Hopkins Road to the Kantor substation, requiring that the existing ROWs be amended in order to accommodate the upgrade project.

The estimated cost for transmission construction for Alternative Route 1 is $28.8 million, while the cost for ROW acquisition is “TBD.”

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