Undersea transmission cable laying work is underway for the first phase of Vineyard Wind, an array of 62 wind turbines in Long Island Sound some 13 miles south of Martha’s Vineyard. The project will use General Electric Haliade-X turbines, each rated at 13 MW.
The offshore export cables are 220–275 kV AC cables while the inter-array cables are 66 kV AC cables. Offshore export cables are 10-11 inches in diameter and the inter-array cables are 5-6 inches in diameter. They are being buried by jet plow anywhere from 5-8 feet below the seabed.
Typical cable vessel installation speeds range from 330ft – 650ft per hour or around 1-2 nautical miles in 18 hours.
Vineyard Wind alerted mariners operating in the area that its cable-laying vessels would start work in late October.
A construction barge and a materials barge along with two tugs are expected to perform diving operations at ducts to prepare the cables for connection and pull-in to the beach. Six smaller workboats and a crew transfer vessel were expected to assist.
As part of the work, a cable barge was to be towed to site to begin cable laying operations around 700 meters off of a beach on Martha’s Vineyard. Plans called for the cable to be pulled to shore by an onshore winch. Once secured, a vessel will lay and bury the cable away from the beach out to the Cape Poge area.
In early July, Vineyard Wind said that during marine debris removal operations, one of its workboats found an unexploded ordnance sitting on the sand bottom in about 130 feet of water. The ordnance measured 1’ x 4’ and weighed around 1000lbs. Vineyard Wind said it notified the Coast Guard of its find.
Vineyard Wind LLC, is 50% owned by funds of Copenhagen Infrastructure Partners and 50% owned by Avangrid Renewables, LLC.