Three new Minnesota power lines worth $2.2 billion are part of a historic transmission plan approved Monday by the Midwest's grid operator.

The board of the Midcontinent Independent System Operator (MISO) passed a $10.3 billion package of 18 power lines aimed at shoring up grid reliability across several Midwestern states. The projects now will go in front of state regulators.

"This is the largest single, long-range transmission investment package approved to date in the United States," said Mike Schowalter, a senior policy associate at St. Paul-based Fresh Energy, a renewable energy research and advocacy group.

The new MISO buildout in Minnesota would be bigger than CapX2020, a $2.1 billion, decadelong power line project that was completed in 2017. While CapX2020 was largely built in Minnesota, its price tag included projects in other Upper Midwest states.

The largest project approved for Minnesota would be a $970 million, 150-mile line from the Iron Range to Benton County in the central part of the state. Duluth-based Minnesota Power and Maple Grove-based Great River Energy would build and own that line.

"This project is the next step to support resiliency and reliability in the northern part of the state," said Josh Skelton, Minnesota Power's chief operating officer. "It brings more ability to bring on more renewable energy resources."

MISO also approved a $689 million power line from north of Mankato east into Wisconsin and a $574 million line that would run from Big Stone, S.D., to Alexandria and then jog southeast.

Minneapolis-based Xcel Energy would build and own $1.2 billion to $1.5 billion worth of the Upper Midwest projects approved Monday by MISO.

These investments would be separate from the $500 million that Xcel has proposed for a line from Becker to near Marshall in Lyon County.

Under the MISO plan, several lines also are planned for Wisconsin, and another would be built in North Dakota. Several power providers are expected to take part in the Upper Midwest projects, including Fergus Falls-based Otter Tail Power and Dairyland Power Cooperative in La Crosse, Wis.

The lines would come into service between 2028 and 2030.

The Minnesota transmission projects would need the blessing of the state Public Utilities Commission (PUC). Power lines — ultimately paid for by electricity customers — are often controversial, and the regulatory process could play out over many months.

Costs for the transmission buildout would be picked up by customers throughout MISO's north central footprint, which covers all or parts of nine states, utility executives say. Several of the proposed power lines would run along existing power line corridors.

Indiana-based MISO is a nonprofit that operates the grid and plans regionwide transmission initiatives. Its members include utilities, transmission owners and various stakeholder groups, including regulators and environmental groups.

"This isn't just MISO coming out with a portfolio on its own," said Priti Patel, Great River's chief transmission officer. Monday's announcement represents several years of planning, and the Minnesota lines will benefit the entire Midwestern electric grid, she said.

"These lines don't just serve Minnesota," Patel said. "They provide benefits that transcend the state."

The $10.3 billion plan approved by MISO's board is expected to be the first of four "tranches" of new power lines in the 15-state MISO region, which extends as far south as Louisiana.

The package announced Monday includes new power lines in Iowa, Illinois, Indiana, Michigan and Missouri. MISO's effort is aimed at improving overall grid reliability and better integrating new wind and solar projects.

The MISO grid is facing high levels of congestion, including in southern Minnesota. Over the past year, wind turbines there have increasingly been temporarily shut down because of a lack of power line capacity.

The new MISO transmission projects are aimed at improving power flows throughout the grid as the region transitions from fossil fuels to renewables.

This spring, MISO warned of potential rolling blackouts after disclosing it faced a shortfall in power generation capacity for the summer in its north and central regions. A key underlying cause: New capacity from renewables isn't keeping up with lost capacity from retiring coal plants.

The CapX2020 project and several other regional transmission buildouts commissioned by MISO freed up a lot of new capacity for renewable power in the 2010s. There was a land-rush of sorts to connect far-flung renewable projects to the grid, but by 2020, increasing transmission congestion had set in.