Central Maine Power Company, a subsidiary of Iberdrola USA, is building or replacing 450 miles of lines, connecting to the New England grid in the south and Canadian transmission lines in the north.
The project includes five new 345kV substations.
The company said the project, called the Maine Power Reliability Program, is the largest energy infrastructure project in Maine’s history. It is also Maine’s first grid update in 40 years, Iberdrola said.
Iberdrola USA’s chief executive, Bob Kump, described the project as "a foundation for the development of renewable energy".
The lines will pass through 75 cities and towns, and is due to finish in 2015. Iberdrola said the project will support up to 2,000 jobs annually.
Iberdrola, has said it will spend $6billion on US wind power between now and 2013.
At least one project in Maine has been put on hold in recent years due to a lack of transmission capacity. In July the state had 200MW of installed wind capacity.