Why is MISO performing Long-Range Transmission Planning (LRTP)?
The Reliability Imperative is the term MISO uses to describe the shared responsibility that MISO, its members, and states have to address the urgent and complex challenges to electric system reliability in the MISO region. MISO’s response to the Reliability Imperative consists of a host of interconnected initiatives that aim to address the region’s challenges in a comprehensive and prioritized fashion. These initiatives are organized into four primary pillars and LRTP is a key component of the Transmission Evolution pillar.

LRTP is needed to determine how transmission can help to ensure a reliable future system as the resource portfolio shifts. The need for LRTP is urgent, given the resource changes already happening, the speed of portfolio change desired by many of MISO’s members, and the length of time it takes a transmission project to go from concept to reality. Not only is there an increased urgency to identify future transmission solutions, but these solutions must also holistically address the needs of the MISO region.

Tackling these future energy needs requires a larger regional approach. LRTP looks comprehensively at MISO’s region and is very much a collaborative effort with stakeholders.

Why did MISO develop a hypothesis map and how will it be used during the study effort?
In developing LRTP Tranche 1, MISO began with an initial roadmap of potential transmission solutions, including solutions required to enable Future 3. These potential lines were adjusted, added, removed, and improved throughout the study process. In the same manner, the hypothesis map initially shared in December 2022 provides a starting point for Tranche 2 studies and includes ideas for potential solutions that address issues in the Midwest Subregion. The map does not represent final projects or a final portfolio. Qualitative considerations created a framework for the hypothesis, including:

    • Resource fleet evolution
      • Deliver future remote renewable resource output to load
      • Facilitate conventional generation resource retirements
    • Operational considerations
      • Internal transfer capability to enhance operating flexibility
      • External transfer capability for mutual support during extreme weather and events
    • Demand side requirements
      • Demand and energy growth driven by electrification

The hypothesis map was then created based on knowledge gained from:

    • Prior Futures siting results
    • LRTP Tranche 1 analysis, including projects discussed but not included in Tranche 1
    • Stakeholder discussions throughout and since LRTP Tranche 1
    • Consideration of long-term LRTP vision (inclusive of Tranche 3 and 4)

The map will continue to evolve as MISO engages with stakeholders, performs analysis, assesses new issues and analyzes substitute alternatives as needed.

Why is MISO considering 765 kV and High-Voltage Direct Current (HVDC) and what are the benefits and concerns with these technologies?
Higher voltage transmission like 765 kV and HVDC provide efficiency and reliability benefits in the transport of electricity over long distances. As the resource fleet continues to evolve, 765 kV and HVDC lines may be more effective in delivering electricity from areas with a high potential for renewable generation to areas of high electricity demand. MISO will consider a combination of 345 kV – 765 kV and HVDC lines when studying projects for Tranche 2. 

Both 765 kV and HVDC transmission lines have much greater capacity than 345 kV and lower voltage transmission lines. This higher capacity results in lower cost per MW of capacity and lower Right of Way (ROW) usage per MW of capacity.

There is minimal 765 kV and HVDC infrastructure in the MISO footprint, and strategies for spare equipment, redundancy during line outages, and the impacts on operations must be considered before the technology is implemented. Additionally, while MISO already oversees the operation of 765 kV lines, additional work needs to be completed for the MISO market to effectively dispatch HVDC lines.

How is MISO considering interregional coordination in Tranche 2?
As with the LRTP Tranche 1, MISO will coordinate with neighboring Regional Transmission Operators (RTO) and Transmission Owners (TO) to ensure awareness of projects as needed and to address underbuild or other needs that impact the feasibility of Tranche 2 projects. MISO anticipates addressing larger interregional issues in later LRTP Tranches.


How will the anticipated FERC Order, based on the 2022 Transmission Planning Notice of Proposed Rulemaking (NOPR), affect Tranche 2 and other tranches?
MISO continues to evaluate the potential requirements in FERC’s NOPR. MISO believes its processes are generally aligned with the Commission’s overall goals regarding the need for robust long-term transmission planning. MISO will update stakeholders on any impacts to the LRTP process if and/or when a rulemaking is released by FERC.

At the November 2022 Planning Advisory Committee (PAC) meeting, MISO stated that the ideas map represents approximately $20 – 30 billion of transmission. What does MISO think the final Tranche 2 portfolio will cost?
MISO is not working through the Tranche 2 process with a specific spending goal in mind. MISO remains focused on pursuing projects that address future grid issues and provides the most value to customers.

How many LRTP Tranches does MISO expect to pursue?
LRTP solutions are being developed in tranches or phases of effort, allowing solutions to be targeted to specific subregional needs before building to potential region-wide portfolios. Tranches 1 and 2 are focused on the Midwest Subregion. Tranche 3 will focus on the South, and Tranche 4 will address the North/South interface limit. In July 2022, the MISO Board of Directors (BOD) approved Tranche 1 projects as an addendum to MTEP 21. Tranche 2 planning is underway and the timing for Tranches 3 and 4 will be determined as Tranche 2 approaches completion.

Longer-term, MISO envisions that long term regional planning will become an embedded part of MTEP processes.  This may result in additional Tranches, based on system needs, although MISO does not envision that every analysis will result in a recommended transmission portfolio.

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