A file photo of a ship laying cable in the...

A file photo of a ship laying cable in the Long Island Sound five miles off Norwalk, Conn. (Feb. 25, 2008) Credit: AP

One of three recently installed cables linking Long Island to the Northeast power grid had a fatal fault and has been out of service since July 2009, regional utilities said as they began work to repair it this week.

The Northport to Norwalk, Conn., power line experienced the fault shortly after it went live in May 2008. Neither of the cables' owners, the Long Island Power Authority and Northeast Utilities of Connecticut, had previously reported the problem, which they said has not impacted service.

The cable was one of three installed under the seabed between Northport and Norwalk in 2008 as part of a project to replace seven liquid-filled cables that had been leaking, officials said.

Paul DeCotis, vice president of power markets at LIPA, said because only two cables operate at one time, the third line is considered a backup, so there have been no service disruptions.

He said LIPA won't be on the hook for repair costs because the cable is still under warranty, though a Northeast Utilities spokesman said third-party examiners won't know the cause of the fault, and who must pay for its repair, until an investigation is complete.

LIPA owns just under 50 percent of the cable, which replaced a series of seven under-Sound cables that were taken offline because of outages linked to boat anchors or other strikes and leaking fluid. The old cables were laid atop the seabed; the new ones are buried and will require excavation to raise them to the surface for inspection. Portions of the old cables remain in the water because of hazards in raising them, officials said. Northeast operates the three cables for both utilities.

The new broken cable is under warranty by manufacturer Nexans, which is conducting the work to determine what went wrong and repair it. Frank Poirot, a spokesman for Northeast Utilities, said independent experts will investigate the broken cable once it is pulled up from the sea floor to determine what caused it to malfunction.

It's not the first time a new power cable has seen disruptions because of malfunctions. Last summer, the Neptune power cable, linking Long Island to New Jersey, was knocked offline for 10 to 12 days because of broken equipment at the New Jersey end of the line. DeCotis said excess power on the LIPA system allowed LIPA to continue operating during a peak summer load without major disruptions.

Neptune went offline once before that, DeCotis said.

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