The Lithuanian-Swedish submarine power cable, NordBalt, was shut down for what is expected to be two and a half months for planned repairs.

A story in The Baltic Course said that the repairs include the replacement of onshore cable joints that have been identified as the cause of frequent failures. It said that Lithuanian power transmission system operator Litgrid reports that 31 failures have been registered since the launch of the 700 MW NordBalt power cable in February 2016, including 12 incidents linked to cable joints. The repair work, expected to be completed by the end of October, will see 22 cable joints replaced on the Lithuanian side and 98 in Sweden.

The cable was provided by ABB, which in March 2017 was acquired by NKT. In a press release at its website, ABB outlined the project, which was described as the world’s longest HVDC Light® underground and submarine cable. “The NordBalt HVDC Light link is a joint project of the Swedish and Lithuanian transmission system operators (TSOs), Svenska Kraftnät and LITGRID AB. HVDC Light is an ABB technology for connecting transmission systems using submarine and underground cables. It offers several compelling benefits, including ‘invisible’ power lines, highly compact AC-DC converter stations, low cable and converter losses, and black start capability (the ability to rapidly restore system operations in the event of a systemwide power outage).”

The NordBalt project included “a 2 x 40 km HVDC Light underground cable on the Swedish side, a 2 x 13 km HVDC Light underground cable on the Lithuanian side, and a 2 x 400 km HVDC Light submarine cable across the Baltic Sea,” the report said. The ABB HVDC Light solution has a power rating of 300 kV. It includes two converter stations, “one at Nybro in Sweden and the other at Klaipeda in Lithuania, where the power is converted from AC to DC for transfer in the HVDC Light cable system. The Swedish power grid has a rating of 400 kV AC and the Lithuanian grid a rating of 330 kV AC; the two grids are asynchronous.”

Contacted by WJI, an NKT spokeswoman said that the owner of Nordbalt “has previously communicated that the line will temporarily be shut down due to cable joint repair. We ... (cannot) comment on any contractual terms, including repair costs.”