Presenter: Abishek Penti provided a status update on the Oncor Roscoe area upgrades project.
Project Overview: Oncor submitted the Roscoe area upgrades for RPG review in December 2024, a tier two project with an estimated cost of around $83 million, requiring a CCN with an expected service date of June 2028.
Project Purpose: Address voltage violations as identified by Oncor.
Project Scope: Involves construction and upgrade activities, including a new Oak Spring station, auto transformers, line upgrades, and decommissioning and rebuilding of certain lines.
Study Overview: Used 2024 RTP data and updated loads for the study base case.
Preliminary Results: ERCOT identified voltage violations and power flow violations and assessed four different options, deeming options one and four for further evaluation.
Maintenance Outage Evaluation: Shortlisted options did not show voltage, thermal, or power flow violations.
Load Serving Capability: Both options improved operational flexibility with option four slightly better.
Cost Estimates: Option one estimated at $84.3 million and option four at $133.4 million, both requiring CCN.
Preferred Option: Option one selected due to addressing project needs, meeting reliability criteria, being cost-effective, and improving long-term load capacity.
Congestion Analysis: No new congestion identified within the study area for the preferred option.
Next Steps: EIR report to be posted in the MIS by May.
Q&A: Discussed assumptions regarding flexible loads and transfer capability.
▶️6 - Muscovy and Voss Lake 345/138-kV Project Overview
Overview of the Muscovy and Voss Lake 345/138-kV project presented.
Joint project with Oncor and LCRA TSC.
Tier one project located in Williamson and Milam Counties.
Project aims to resolve thermal violations, provide additional 345-kV sources, further network transmission facilities, and enhance system reliability.
Total combined cost for Oncor and LCRA TSC is just under $382,000,000.
Project includes installation of three new 345/138-kV autotransformers, one 10.4 Mvar capacitor bank, and new transmission lines.
29 miles of new 345-kV double circuit transmission lines and 2 miles of new 345-kV transmission lines to be installed.
Highlight of existing configuration reveals thermal violations mainly at Hutto and Sandow switches due to significant load growth.
Oncor to establish a new Muscovy 345/138-kV switch east of Limmer and Teal Switch, with breaker and a half arrangement.
Construction of Voss Lake 345/138-kV switch north of Sandow with one auto transformer.
Construct 25-mile 345-kV double circuit line from Muscovy to Voss Lake rated 5,000 amps.
Construct 2-mile 345-kV line from Voss Lake to Walleye Creek as a single circuit on double circuit capable structures.
Coordinate construction of a 4-mile 345-kV double circuit line from Limmer to Muscovy rated 5,000 amps.
No questions were raised after the presentation.
▶️7 - ERCOT Independent Review Scope: Muscovy and Voss Lake 345/138-kV Project
Presenter Abishek Penti gave an overview of the project's scope for Oncor and LCRA TSC's Muscovy and Voss Lake 345/138-kV project.
Project classified as tier one with an estimated cost of $381,830,000 and an estimated in-service date of December 2028.
The project's main purpose is to address reliability violations identified by Oncor and LCRA.
Independent review is underway with the use of 2024 RTP 2029 summer peak case as a seed for the study base case.
Consideration of transmission projects with in-service dates on or before December 1, 2028. Other placeholder projects from RTP 2024 will be removed.
Evaluation criteria include thermal ratings, voltage limits, and contingencies P0 to P6 and G-1 and X-1 evaluations on specified generators and autotransformers.
Study procedure involves need analysis, project alternatives testing, planned maintenance outage, and long-term load serving capability assessments.
Congestion analysis and potential sensitivity analyses might be performed as per relevant sections of the planning guide.
Final recommendations are expected by the end of Q3 2025.
Discussion addressed questions on potential inclusion of 765-kV import lines in independent reviews; deemed unlikely due to timelines.
▶️8 - 2026 Long-Term System Assessment (LTSA) Planning
Nelson Avila presented updates to the weather year selection methodology for the 2025 RTP economic study.
The weather year selection is crucial as it determines renewable and load profiles for production cost simulation.
Prior to 2017, ERCOT used a single weather year representing the average of 16 available years.
In 2017, ERCOT developed a methodology to include sensitivity weather years to address weather uncertainties.
The updated methodology now incorporates peak net load and net load demand variables, improving risk capture during peak net load hours.
New metrics now include correlation with location of wind and solar units.
Weather years are now ranked with different scores separating load and renewables compared to the previous single-scoring method.
Flexibility is introduced to select weather years specific to constraints related to renewable generation patterns.
Stakeholder feedback is sought on the new methodology.
Variables used in the new methodology include peak load, demand load, peak net load, and demand of net load.
Renewable generation variables include correlated metrics for wind and solar capacity factors.
A final score is created by averaging renewable and load scores, helping to rank weather years on a heat map.
A difference with the previous methodology is the ranking order of load variables (descending) versus renewable variables (ascending).
Sensitivity weather years are selected to focus on known constraints like Panhandle and West Texas exports.
Question and answer session included queries about distinctions between peak and net load, the methodology's applicability to reliability studies, and adjustments based on DER growth.
ERCOT confirms the 2025 RTP methodology targets economic rather than reliability studies.
Discussion continues on the application of the new methodology to other constraints and potential timeline for implementation.
ERCOT emphasizes that stakeholder feedback will be considered before finalizing the methodology.
