NSTAR Electric Co., doing business as Eversource Energy, filed a petition with the Massachusetts Energy Facilities Siting Board seeking approval to build, operate, and maintain a nearly nine-mile, 115-kV, underground transmission line extending from the company’s Sudbury substation on Boston Post Road (Route 20) in Sudbury to Hudson Light & Power Department’s (HLPD) substation at Forest Avenue in Hudson.
The proposed line, which would travel through the municipalities of Sudbury, Hudson, Stow, and Marlborough — as well as related modifications to the Sudbury substation, including two new 115-kV breakers and a 115-kV shunt reactor — comprise the proposed Sudbury-Hudson Transmission Reliability Project, the company said.
Eversource noted that while not part of the project, HLPD would install three new 115-kV breakers at the Hudson substation to support the new line, and make other related modifications, including reconfiguring the existing transmission lines to a ring bus design.
The company said that the project is necessary to provide a reliable energy supply for Massachusetts, while minimizing cost and environmental impacts. The project is one of about 40 individual transmission projects to emerge from an extended transmission study process conducted by ISO New England (ISO-NE) and its Greater Boston Working Group to identify and address reliability needs of the transmission system that serves much of Massachusetts and southern New Hampshire, Eversource said.
The study process resulted in the issuance of the Greater Boston Area Updated Transmission Needs Assessment, dated January 2015, and the selection of a set of transmission projects, including the Sudbury-Hudson project, as the preferred solution to meet the identified needs, the company said.
ISO-NE in February 2015 made public its preferred solutions to address those needs, which were a series of transmission projects, including the proposed project, the company said.
The primary purpose of the project is to provide additional transmission capacity within the area designated by ISO-NE as the Marlborough Subarea of Sub-Area D, which encompasses the municipalities of Berlin, Framingham, Grafton, Hudson, Marlborough, Northborough, Shrewsbury, Stow, Southborough, and Westborough, the company said.
Certain 69-kV and 115-kV lines serving the Marlborough Subarea would overload under various contingencies at existing peak load levels, which would lead to a voltage collapse and the consequent loss of service to more than 400 MW of load — about 80,000 customers, Eversource said.
The project would address that need with the new 115-kV transmission line, the company said, adding, “In doing so, it will ensure continued compliance with applicable federal and regional transmission reliability standards and criteria, and will maintain reliable electric service to area substations serving the Marlborough Subarea.”
Noting that it evaluated alternative routes, the company said that the project, that is, the about nine-mile, underground route between the Sudbury and Hudson substations, runs primarily along an inactive railroad corridor owned by the Massachusetts Bay Transportation Authority (MBTA).
The route selection process also resulted in a “noticed variation,” which includes an overhead transmission line along the same MBTA corridor as the project, as well as in a “noticed alternative route,” which is about 10.3 miles long and a geographically distinct route that travels underground within public roadways, the company said.
The company noted that it is filing with the state Department of Public Utilities (DPU) a petition for specific and comprehensive zoning exemptions from the zoning bylaws of the towns of Sudbury, Hudson, and Stow in connection with the project, as well as a petition requesting approval of the new line (Section 72 petition). In addition, the company said that it is filing motions with the DPU and siting board, requesting that the DPU refer the Section 72 petition to the siting board and that the siting board consolidate both petitions for its review.