Close to 40 km and 2,500 tons of Nexans’ submarine cables in the Inner Oslo fjord will ensure electricity to “half” of Norway

14 cables weighing one ton per 16 metres. These are huge dimensions and world-class cables being commissioned today by Statnett in the Inner Oslo fjord. The cable system has been made at Nexans' subsea cable factory in Halden and will supply 2.5 million inhabitants in Eastern Norway with electricity for several decades.

Oslo 30. August Statnett is strengthening the power supply in Eastern Norway and commissioned Nexans Norway to replace two old cable systems, which have been operating in the Inner Oslo fjord since 1958 and 1975, with two new, robust submarine cable systems.

Nexans Norway is one of the leading submarine cable manufacturers in the world and designs, manufactures and installs high-voltage subsea cables and offshore control cables suitable for various waters, lengths and sea depths the world over.

Old cables recycled
– During the summer of 2017 and 2018 we recovered and shipped 1,200 tons of old cables for recycling to Norsk Gjenvinning. We then laid and protected 14 new submarine cables on the seabed and connected them to the onshore power grid. “The work has proceeded really well both on land and at sea and it has been an extra bonus to be able to work at home here in the Oslo fjord,” says  Ivar Rolfstad, Project Manager at Nexans Norway. 

Backbone
The submarine cable system in the Inner Oslo fjord forms part of the backbone of the Norwegian power grid.
– “These cable installations under the Oslo fjord are some of Eastern Norway’s most important power connections and make a major contribution to safeguarding the power supply, particularly on the coldest winter days,” says Martin Mauritzen, Project Manager at Statnett.

About the Inner Oslo fjord project:
For the Inner Oslo fjord project, Nexans Norway AS has provided engineering, production and installation of two 420 kV submarine cable systems, a total of 14 individual cables. The first seven cables were installed between Solberg (Hurum) and Brenntangen (Vestby) in the summer of 2017 and the last seven cables between Filtvet(Hurum) and Brenntangen (Vestby) in 2018.

Facts about the submarine cables:
The 420 kV HVAC submarine cable system is the most state-of-the-art technology available on the market today.
o Diameter: 15 cm, weight per metre: 61 kg. 
o A total of 14 cables have been laid: seven at 3 km between Solberg (Hurum and Brenntangen (Vestby) and seven at 2.4 km between Filtvet (Hurum) and Brenntangen. A total of approx. 38 km cables.
o The cables are protected against anchors and fishing equipment by Nexans’ Capjet subsea trenching system, which buries the cable in the seabed so that it is hidden from view and well protected.

World records
Nexans delivered the first 420 kV HVAC PEX cable system in the world at Ormen Lange in 2006 and set two world records north of Bergen in 2016 with the deepest and longest cable of this type in the world – 20 km down to a sea depth of 390 metres. In 2019, new records will be set when the same system is installed at a depth of 530 metres in the same area – Fensfjorden, north of Bergen.

Nexans har hatt mange båter og folk i sving i Oslo-fjorden våren og sommeren 2017 og 2018
Several boats and people from Nexans were in activity in and by the Oslofjord during spring and summer 2017 og 2018.

For å beskytte kablene mot anker og fiskeredskaper er de beskyttet med Nexans sitt spesialsystem som spyler kabelen ned i havbunnen

The cables are protected against anchors and fishing equipment by Nexans’ Capjet subsea trenching system.  Foto: Nexans

De nye Indre Oslofjord-kablene er produsert av Nexans’ fabrikk i Halden
The new Inner Oslofjord cables were produced at Nexans Halden. Foto: Nexans

Det var STK som produserte de gamle sjøkablene - operasjonen mellom Son og Filtvedt i 1959
The old submarine cables were produced by STK, today's Nexans Norway. They have been in commission for half a centry. Here a picture from the installation activities between Son and Filtvet in 1959.  Photo: Leif Ørnelund  Oslo Museum