Project developers, policymakers and think tanks working in the capital-intensive arena of energy development say a new Montana-North Dakota high-voltage transmission line could be a game changer for an area of the American West that’s seen limited expansion to its power grid in four decades. The North Plains Connector Line would be the region’s first major grid expansion since the construction of a 500-kilovolt line that carries power from the Colstrip coal-fired power plant to population centers in the Pacific Northwest in the early 1980s.