"Whereas overhead lines can generally  be repaired in the course of a few hours or days, subsea cables generally take months to fix. Statnett is one of the European system operators with the most extensive use and experience of subsea cables, and all of the company's major subsea cable interconnections have been out of operation for long periods of time due to faults. This includes Statnett's new subsea cable between Norway and the Netherlands, which has been out of operation for several months. 

   
Statnett has built the world’s longest subsea DC interconnector to the Netherlands, and the world's first cable using plastics as insulation (PEX cable) of 420 kV to Nyhamna, and we have also had 420 kV cables crossing the Oslofjord for decades.
 

Many European companies are far more sceptical than Statnett. For example, Aftenposten on Thursday quoted the Danish company energinet.dk which will not use cables on long distances for the highest voltages due to technical reasons. 

The recently published ten-year plan from ENTSO-E (European Network of Transmission System Operators for Electricity) states that cables should only be used in very special circumstances, for the following reasons: 

• high costs; 5-20 times higher than for overhead lines, depending on local conditions 
• security of supply; particularly in light of the risk of repairs taking a long time
• systems-related issues, such as problems connected to reactive conditions, resonance and stability. 
  

Faults have not only occurred on the Oslofjord cables, although these are the most recent. And Statnett does not agree to the allegations that these faults were due insufficient maintenance. Statnett's maintenance programmes are based on recommendations from the suppliers and the knowledge and experience available to us. This applies to our own experience as well as those of national and international cable owners and suppliers. Statnett has fully complied with this maintenance programme and carried out weekly, monthly and yearly inspections of the cable installations.

"The allegations in Bergens Tidende today concerning insufficient maintenance are simply not correct," Akselsen says. "Statnett cannot see that the faults that unfortunately occurred were in any way related to this. It is a point of fact, however, that faults and incidents may happen, even when the recommended and established routines have been followed. We have reported back to the authorities about this, and so far no conclusions have been reached in this case.  Faults can happen regardless. And when they do, repairs take a long time."