Oncor Electric Delivery Company and Brazos Electric Power Cooperative on Dec. 11 filed with the Public Utility Commission (PUC) of Texas an application for a certificate of convenience and necessity regarding a new, single-circuit, 138-kV transmission line to be built on double-circuit capable structures between the existing Oncor Cogdell substation in Scurry County and the existing Brazos Electric Clairemont substation in Kent County in Texas.
Following final PUC approval of the proposed project, Oncor and Brazos Electric have agreed to negotiate in good faith to determine an appropriate location along the approved route for a division of ownership between Oncor and Brazos Electric that will generally divide the line in two even parts. The companies added that they have agreed that each party will be responsible for their respective portions of the proposed project with coordination of those activities between the two parties.
The project includes modifications at Brazos Electric’s Clairemont substation, the companies said, noting that station modifications to accommodate the proposed project at Oncor’s existing Cogdell substation are being performed under another project and are therefore not included in this project.
The length of the line ranges between about 22.7 miles to 33.4 miles, depending on which route is selected by the PUC, the companies said.
The proposed project area is situated across portions of southwestern Kent and northern Scurry counties, with most of the project area located in rural and undeveloped lands. The major roadway corridors in the area US Highway 380, State Highway (SH) 208, and Farm-to-Market (FM) 1142. No towns or cities are present within the project area, the companies added, noting that residential development within the project area is minimal and limited to rural and large tract properties scattered throughout the project area.
Agriculture is an important segment of the economy throughout the region and primarily represented by cropland, pastureland, and ranchland, the companies said, adding that numerous oil and gas facilities are located within the project area.
Discussing the need for the proposed project, the companies noted that currently, the Brazos Electric Salt Creek substation, located in Kent County, south of the City of Spur, serves about 60 MW of load. Salt Creek is served by the 22-mile, 138-kV line from Brazos Electric’s Scurry switching station in Scurry County, and the 17-mile, 138-kV line from American Electric Power’s (NYSE:AEP) Spur switching station in Dickens County. The companies added that transmission sources to that area are from Oncor’s Sun switching station connected to the Scurry switching station and from AEP’s Aspermont and Paint Creek switching stations connected to the Spur switching station.
The lack of operational flexibility when multiple transmission facilities are taken out of service is an increasing problem in West Texas, the companies said, adding that due to increasing load levels, the ability to take facilities out of service for scheduled clearances, maintenance, or testing is limited by unacceptable voltage and thermal loading conditions caused by the next contingency.
Steady-state power flow analysis indicates that adequate voltage cannot be maintained in the area after P6 contingencies (two overlapping single contingencies) under certain NERC reliability criteria without significantly reducing the load at Salt Creek. The companies also said that studies have shown that loss of either the Sun-Scurry Switch or Scurry Switch-Salt Creek 138-kV line sections, followed by loss of any line section along the Paint Creek-Aspermont-Spur 138-kV line, results in an unsolved contingency during power flow analysis. That is an indication of potential voltage collapse in the area, and such a scenario would result in loss of service to all customers served on those transmission lines, the companies said.
Construction of the proposed project would strengthen the transmission system by creating a new 138-kV source to the Salt Creek area, the companies said, adding that the resulting 138-kV system would become more networked to support voltage conditions and alleviate thermal overloads during single forced or planned outages on different sections of the area transmission lines.
In addition, the proposed project would improve operational flexibility during emergency conditions, while obtaining clearances for equipment maintenance, and when connecting new loads to the system, the companies said.
Noting that they retained AECOM to prepare an environmental assessment and routing study, Oncor and Brazos Electric said that Oncor, in coordination with Brazos Electric, selected “Route 125” as the route that best addresses certain requirements.
According to the filing, Alternative Route 125 is about 22.7 miles, which is about 10.7 miles shorter than the longest alternative route included in the application. Among other things, the filing noted that that route:
- Has the highest percentage (80.4%) of its route that parallels existing corridors than any other alternative route
- Has one habitable structure within 300 feet of its centerline over its entire length
- Crosses no recorded cultural resource sites
- Crosses the Double Mountain Fork Brazos River parallel to an existing road corridor, thereby minimizing the impact to that ecologically significant stream segment, as designated by the Texas Parks and Wildlife Department
Oncor’s portion of the estimated total project cost for Route 125 is about $10.2m, while Brazos Electric’s portion is about $12.2m, according to the filing.
According to the estimated schedule, right of way (ROW) and land acquisition, as well as engineering and design, are set to begin in December 2018 and be completed in September 2019; material and equipment procurement is set to begin in August 2019 and be completed in February 2020; and construction of the facilities is set to begin in January 2020 and be completed in June 2020, which is also when the facilities would be energized.