Pedernales Electric Cooperative (PEC), in an application to amend its certificate of convenience and necessity filed on June 2 with the Public Utility Commission (PUC) of Texas, said that it is proposing to rebuild and upgrade the Highway 32-Wimberley 69-kV transmission line to a single-circuit, 138-kV transmission line to relieve the loading on the 138-69-kV autotransformer and 69-kV transmission line.
PEC said that its existing four-mile, 69-kV radial transmission line connecting its existing Highway 32 substation to its existing Wimberley substation and associated 138-69-kV autotransformer are the primary sources of electricity for the Wimberley area. The Highway 32-Wimberley 69-kV line is also relied upon for backup capacity for distribution ties to the Highway 32, Dripping Springs, Rutherford, and Fischer substations, PEC said.
The proposed project – which is located in Hays County – would begin at the existing Highway 32 substation, located north of the intersection of Farm-to-Market (FM) road 32 and FM 12, and extend to the existing Wimberley substation, located west of FM 2325 in Wimberley, Texas, PEC said.
The entire project – which is not located, all or in part, within a competitive renewable energy zone (CREZ) – would be about four to five miles in length, and is estimated to cost between about $5.4m and $12.1m, depending on the final route approved by the PUC, PEC said.
PEC noted that it selected steel (weathered) monopoles with braced post insulators for the proposed project. The proposed routes are parallel to, and west of, FM 12 from the intersection of FM 12 and FM 32 to the City of Wimberley, PEC said, adding that the area traversed by the line is in the Edwards Plateau and the Balconian biotic provinces of Texas. The southern half of the project crosses rural hill country land used for pasture/rangeland, while the northern half of the project crosses the suburban, residential area south of Wimberley, including crossing the Blanco River, PEC said.
Discussing the need for the proposed project, PEC said that the 138-69-kV autotransformer located at the PEC Highway 32 substation is nearing thermal capacity, and it will reach its thermal capacity of 44.8 MVA in winter 2024. The Highway 32-Wimberley 69-kV, 4/0 ACSR transmission line serves as the primary source of electricity delivered to consumers in the Wimberley area and provides a backup source of power to adjacent substations, including Dripping Springs, Rutherford, Highway 32, and Fischer substations, PEC said.
At a projected winter 2021 load of 42.4 MVA using the existing 69-kV voltage classification, neither the existing transmission line, nor the existing autotransformer are able to provide backup capacity to support the approximate 15 MW backup capacity necessary to support power restoration from a potential single distribution feeder outage at either the Rutherford or Highway 32 substations, PEC said.
Furthermore, PEC noted that the Wimberley area has experienced a significant growth over the last several years and as load continues to increase, PEC’s ability to meet reliability standards and maintain reliable electric service to the Wimberley area becomes more challenging with the existing facilities.
To support the transmission line voltage upgrade, substation improvements would be required at the existing Highway 32 substation, and the existing Wimberley substation. Upgrades to the Highway 32 substation would include removal of the 138-69-kV autotransformer and associated 69-kV circuit breaker, PEC said, adding that the Wimberley substation only requires upgrades to the transmission line terminal, and protective relay upgrades.
Discussing a routing study, PEC said that, among other things, that it determined that “Route C” provides the best balance of routing characteristics and best addresses certain requirements. PEC said that Route C, for instance:
- Is the shortest route, at 3.9 miles
- Has the fewest habitable structures within 300 feet of the right of way (ROW) centerline, with 109
- Has the longest length of ROW using existing transmission line ROW, at 3.9 miles (100%)
- Is tied with two other routes for having the second fewest number of stream crossings, at five
- Crosses no parks/recreational areas
- Has no cemeteries within 1,000 feet of the ROW centerline
- Crosses no recorded archaeological sites
Among other things, PEC said that according to the estimated schedule, if the project is approved, then ROW and land acquisition – as well as engineering and design – would begin in July 2018, and be completed in March 2019; material and equipment procurement would begin in December 2018, and be completed in March 2019; and construction of the facilities would begin in September 2019, and be completed in December 2019, which is when the facilities would be energized.