Dive Brief:
- The Midcontinent Independent System Operator and the Southwest Power Pool are considering two sets of 500-kV transmission projects that would provide reliability, economic and transfer benefits across their southern seam, according to a draft report discussed Friday.
- The potential projects grew out of the SPP-MISO 2024-25 Coordinated System Plan study, which aimed to find transmission projects that would benefit both systems along their border in Arkansas, Louisiana, Oklahoma and Texas.
- SPP and MISO are taking comments on the draft report and could seek approval of a final set of transmission projects late this year or in early 2027.
Dive Insight:
The CSP study identified two potential sets of transmission projects: one called Core that would cost about $1.3 billion and one dubbed Core+ that would cost about $3.6 billion.
The Core+ projects fix more MISO and tie‑line reliability issues and deliver the greatest 2034 congestion relief, especially in SPP, while providing “moderate” import capability gains, the grid operators said in the draft report. The projects would increase MISO’s average import capability by 3.4 GW and SPP’s by 1.1 GW, they estimated.
The projects also address issues at larger scale immediately and appear to have a higher reliability and economic impact than the Core projects, according to a Friday presentation to the SPP-MISO Interregional Planning Stakeholder Advisory Committee.
The Core combination emphasizes import capability, especially into MISO, resolves fewer MISO/tie‑line issues but more in SPP, and delivers lower congestion relief than Core+, the grid operators said. It would boost MISO’s average import capacity by 2.6 GW and SPP’s by 1.5 GW.
Compared to Core+, the projects can more easily be expanded as the grid system evolves, and they preserve optionality amid rapid load growth, the grid operators said.
“The recommended CSP study solutions provide meaningful reliability improvements, expanded bi‑directional transfer capability, and material congestion relief that collectively support RTO and stakeholder objectives,” SPP and MISO said.
MISO and SPP asked stakeholders for their opinions on the proposals. The grid operators said they would review those comments as they consider their next steps. Depending on that review, they may seek tariff “enhancements” for interregional cost allocation, with a potential filing at the Federal Energy Regulatory Commission in the second half of this year.
Also, SPP and MISO said they would seek a signoff from their Interregional Planning Stakeholder Advisory Committee, as well as approvals late this year or early next year at SPP’s Markets and Operations Policy Committee and MISO’s Planning Advisory Committee, and both RTO boards.
The Clean Grid Alliance is “cautiously optimistic” about the direction of the study, “but there’s a long way to go,” Beth Soholt, CGA executive director, said in an email. “The effort will be successful when we have the right set of projects identified with a good business case, cost allocation, and utilities wanting to build. Steel in the ground is the ultimate success!”
In July, FERC on a 2-1 vote rejected a request by SPP and MISO that they be allowed to expand the analysis they conduct during the CSP study.
The CSP study process has never identified an interregional project that would benefit both MISO and SPP because of the limited benefit valuations that are delineated in their joint operating agreement, according to their Jan. 15 waiver request.
