NSTAR line to boost capacity to Cape Cod, resolve constraints

NSTAR Electric, a Boston-based utility subsidiary of Northeastern Utilities (NYSE:NU), will begin construction of Lower SEMA, a 26-mile, 345-kV transmission line on Cape Cod at the end of this month. The $106m project will change the region’s power landscape by resolving constraints to backup power options and improving Cape Cod’s access to a diverse power portfolio. 

“The project has been in the planning stages for several years,” an NSTAR spokesperson told TransmissionHub Sept. 17. “Its purpose is primarily to help NSTAR in the region to meet the federal requirements for a third redundancy of power to serve the Cape.”

The system upgrade will include development of the new line, beginning in Carver, Mass., and terminating in West Barnstable, Mass., as well as separation of an existing double-circuit line and certain station improvements.

“This development plan allows NSTAR to use an existing 115-kV transmission line that goes roughly from the Cape Cod Canal to the Town of Barnstable as a 345-kV line, as it was originally designed,” the spokesperson said. “It’s going to provide much greater capacity right into the center of Cape Cod.”
Currently, NSTAR uses the Sandwich, Mass.-based Canal Generating Station, a petroleum-based generator, as the area’s third backup power option.

“In a study that was done by ISO New England, they determined that the best option for third backup would be a new line, such as the one NSTAR is building, that comes over the canal,” the spokesperson said. 

Costs for this regional transmission project will be recovered through charges to end users throughout New England. The amount of any given regional increase will vary, but NSTAR’s spokesperson noted that the utility’s residential customers could see about $0.11 added to an average monthly bill of 700 kWh. Some of those costs, however, should be offset for NSTAR’s customers.

 “Right now the folks in that area are paying uplift charges for the Canal station to operate as that third redundancy,” the spokesperson said, “and those uplift charges go away if that plant is no longer needed for that purpose.”

Energy from the proposed 468 MW Cape Wind offshore wind farm in Nantucket Sound could be among the new power generation options for Cape Cod in the future, but NSTAR’s spokesperson said that that outcome is not NSTAR’s motivation for developing the line. “As it relates to Cape Wind, the line is actually neutral,” he said.

“There is some thought that if the project does come to pass, the new line would give the developers another outlet to move the power from the project.”

The utility expects the transmission system upgrade to be completed by summer 2013.