Massachusetts regulators approve NSTAR 115-kV transmission line

Massachusetts state regulators, in an April 2 order, granted NSTAR Electric’s — now Eversource Energy — petition seeking approval to build and operate the new 7.8-mile, 115-kV overhead transmission line along an existing right of way between the Barnstable switching station and the Harwich Tap, according to TransmissionHub.

The company filed its petition in February 2014. The transmission project involves building a new segment of 115-kV line — to be known as Line 139 — that will be supported on about 62 new steel monopoles installed over about 7.8 miles of the existing ROW in Barnstable, Yarmouth and Dennis, the state Department of Public Utilities (DPU) added in its order.

The company proposes to leave the existing Lines 118 and 119 in service, which would result in three 115-kV lines supplying power to the area of Cape Cod from Yarmouth to Provincetown, including the towns of Yarmouth, Dennis, Brewster, Harwich, Chatham, Orleans, Eastham, Wellfleet, Truro, Provincetown and Nantucket — collectively, the Mid/Lower Cape.

The proposed new Line 139 will connect to the existing section of Line 119 at the Harwich Tap forming Line 139 from the Barnstable switching station to the Orleans substation with a tap to the Harwich Bulk substation, the DPU added. Line 119 will only serve Harwich and will no longer serve Orleans, while Line 118 will only serve Orleans.

The company maintains that the project is needed in order to address transmission reliability concerns for customer loads east of Barnstable, the DPU added.

The company’s conceptual grade cost estimate (-25 percent/+50 percent) for the project is $19.5 million, the DPU said, noting that the construction is anticipated to take six to nine months, beginning early this year.

Discussing need for or public benefit of use, the DPU noted that the primary transmission system on Cape Cod is a 115-kV system that runs west to east, with the system located east of the Barnstable switching station categorized as a radial transmission system. Two radial lines, Lines 118 and 119 originate at the Barnstable switching station and terminate at the Orleans substation and generally supply all load east of Barnstable.

Lines 118 and 119 serving the Mid/Lower Cape largely share double circuit towers, so that a single incident could cause a loss of electric service to the Mid/Lower Cape customers. Lines 118 and 119 also extend from the Harwich Tap in Dennis to the Harwich Bulk substation, and supply the Harwich Bulk and the Lothrop Avenue substations, both located in Harwich, the DPU added.

The company determined the total load supplied by Lines 118 and 119 serving the Mid/Lower Cape by adding the peak loads at the Harwich Bulk, Orleans and Wellfleet substations, plus the entire load on Nantucket Island. While Nantucket is served by National Grid plc’s National Grid USA, Eversource is required to provide 50 percent of Nantucket’s load from Lines 118 and 119 on a firm basis, and possibly the entire load in the event of a contingency.

The average annual load of the Mid/Lower Cape is projected to grow 1.3 percent, net of reductions from forecast energy efficiency. Lines 118 and 119 serve about 84,500 customers, if Nantucket is included.

Given that the Mid/Lower Cape is a radial system, the company said that the number of customers whose service could be interrupted by the simultaneous loss of Lines 118 and 119 is not a function of current or anticipated load levels.

The company said that the simultaneous loss of Lines 118 and 119, which is considered a single (N-1) contingency, would cause the entire Mid/Lower Cape to be out of service, as well as the Nantucket load served by the Lothrop Avenue substation.

The company concluded, the DPU added, that the construction of the proposed Line 139 would increase reliability and address the loss-of-load impacts associated with the simultaneous loss of Lines 118 and 119, which could affect 84,500 customers and more than 200 MW of related peak loads.

Based on, for instance, the configuration of the system as radial, combined with the geographic isolation of the Cape Cod transmission system and the potential for the loss of service for about 84,000 customers, the proposed project would increase reliability of the Mid-Cape system, the DPU said. Accordingly, the DPU said, it finds that there is a need for the project, and that by meeting that need and providing other electrical system benefits, the construction and operation of the project would result in public benefits.

Among other things, the DPU said that the land use impacts would be similar to the existing impacts along the ROW, as the project would occur entirely within an existing transmission and distribution ROW. Construction impacts near certain cultural and historical resources would be avoided by adhering to the “Archeological Avoidance Plan and Construction Methodology.” The DPU also said that it has been determined that the project, as proposed, would not result in a “take” of state-listed species.

The visual impacts of the project would be minimal. The DPU further noted that the project would result in alterations and impacts to jurisdictional wetland resources, adding that the company is obtaining necessary permits and orders for construction activity in those areas. The company would minimize wetland and water resource impacts by creating a stormwater pollution prevention plan.

The DPU added that the company is to, among other things, begin project construction within three years of the order’s date.

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