Minnesota Power, the biggest utility in northern Minnesota, on Wednesday formally started the regulatory process to build a 350-mile power line that could cost up to $650 million, a project so big it has its own name — the Great Northern Transmission Line.

The line has been under development by the Duluth-based utility since 2012 after it struck an innovative deal with Manitoba Hydro to balance out wind power it is generating in North Dakota with water power from the Winnipeg-based firm. Minnesota Power filed route permit applications with state and federal authorities Wednesday.

The transmission line will have the capacity to move at least 750 megawatts of electricity generated by Manitoba Hydro, which operates 15 hydropower generating stations in the province and exports about one-third of its power to the U.S.

Minnesota Power, a unit of Duluth-based Allete Co., has agreed to buy about 250 megawatts from Manitoba Hydro. The steady power of the Manitoba hydroelectric dams will serve as a backup to intermittent wind power generated at Minnesota Power's wind farms in North Dakota.

In turn, when Minnesota Power's wind generation is greater than it needs, the excess will flow to Manitoba. The rest of the capacity on the line may be used by Manitoba Hydro to send electricity to other customers in the U.S.

"The Great Northern Line enhances a unique synergy involving hydropower and wind," Brad Oachs, chief operating officer for Minnesota Power, said in a statement. "The new transmission capacity more readily allows the Manitoba Hydro system to store intermittent wind generation during times when energy markets don't need it."

The line will stretch from Winnipeg to a Minnesota Power substation in Blackberry, Minn., near Grand Rapids, when it is finished around 2020.

Two routes are being considered, the utility said, and both follow existing right of way for transmission lines. The Minnesota Public Utilities Commission, following input from the public and interested parties, will decide the route next year.

The cost of the line will depend on the final route, Minnesota Power said. A preliminary estimate last October put construction cost in a range of $406 million to $609 million. A spokeswoman for Minnesota Power, Amy Rutledge, said the utility started to "get a better picture" of the cost as more development work was done over the past six months. Minnesota Power and its customers ultimately will pay only for the portion associated with the amount of electricity the utility gets from Manitoba Hydro, she noted.

The company for the past two years met state and federal agencies, local governments, tribes and landowners in northern Minnesota to discuss the proposed line. Executives gave it a name to help people understand the project. While there was once a railroad from St. Paul to Seattle called the Great Northern, the name for the line comes from a utility called Great Northern that merged with Duluth Edison in 1923 to form Minnesota Power.

"As we were meeting with people and getting input, naming the line helped them right away know what we're talking about," Rutledge said. "It's a great identifier."

She said the company's other transmission lines have acronyms and numbers related to their voltage or some other characteristic. Minnesota Power's line from its North Dakota wind farm to Duluth, for instance, is simply called the DC line, short for direct current.