The Bureau of Land Management (BLM) will be the lead federal agency for the federal permitting associated with the North Gila-Imperial Valley #2 (NG-IV#2) Transmission Project, and that is expected to be initiated this year, Southwest Transmission Partners, LLC told the Arizona Corporation Commission on Jan. 27.
The line would run from the existing North Gila 500-kV substation northeast of Yuma in Yuma County, Ariz., into California, where it would interconnect to the existing Imperial Valley 500-kV substation southwest of El Centro in Imperial County, Southwest Transmission Partners said.
About seven miles of the 90-mile project would be located in Arizona – as currently proposed and within an existing BLM-designated corridor, Southwest Transmission Partners said, adding that the portion of the line in Arizona would parallel existing/approved lines.
The NG-IV#2 project has been actively involved with the Southwest Area Transmission, WestConnect and California ISO transmission planning forums, Southwest Transmission Partners said.
The voltage of the project – which is planned to be in service in December 2021 – would be 500-kV, single or double circuit, and may also include 230 kV, according to the filing.
According to TransCo.Energy, LLC’s February 2016 “WECC Path 46 Rating Increase Comprehensive Progress Report” that was included with the filing, the proposed project’s plan of service includes: a new 500-kV substation – the Highline 500-kV substation – to be located adjacent to the Imperial Irrigation District’s existing 230-kV Highline substation at Holtville, Calif.; a new 1120 MVA, 500/230-kV transformer at Highline; a new 55-mile 2x 2156 ACSR 500-kV line from the North Gila 500-kV switching station to Highline with 70% series compensation; and a new 35-mile 2x 2156 ACSR 500-kV line from Highline to the Imperial Valley 500-kV substation.
The report noted that the analysis was prepared to include only a 500-kV single circuit as the initial buildout of the project, and that additional sensitivities during a Phase 2 analysis may be examined as the project development progresses to co-locate planned 230-kV facilities in the region.
According to the report, the study was conducted using the Western Electricity Coordinating Council (WECC)-approved 2018-2019 heavy autumn power flow model that was previously used for the Hassayampa-North Gila #2 Project’s path rating study as the starting base case; analysis performed as part of the study included power flow, transient stability and post-transient stability.
The starting base case had these new 230-kV circuits replacing Imperial Valley-El Centro 230-kV in the definition of the WECC’s West of Colorado River Transmission Path (WOR):
- Imperial Valley-Fern 230-kV line
- Imperial Valley-Dixieland 230-kV line
- Imperial Valley-Lambert 230-kV line
The report added that the starting base case was updated to include the Harry Allen-El Dorado 500-kV line.
The report noted that the studies showed that the proposed project can achieve a total transfer capability of at least 1,330 MW following the full implementation of the project’s plan of service, while meeting NERC reliability standards and WECC system performance criteria.
According to the report, the proposed project would become an additional component of the WECC’s WOR, and it is expected to provide a significant increase in transmission capacity between Arizona and southern California.
Among other things, the report said that additional benefits that may be derived from the project include providing an increase in diversity of the regional energy resource zones; providing an increase in reliability and import capability to the Southern California Import Transmission system; and enabling efficient use of existing transmission corridors.