– This is an important step towards securing the supply of electricity, says Elisabeth Vike Vardheim, Executive Vice President in Statnett.

The current cables between Sogn and Ulven substations are from the 1950s and 60s, and the condition of the cables are not satisfactory. Even with the levels of electricity consumption we see today, an error on one of the existing cables, combined with subsequent errors somewhere else, will cause a power outage for up to 1000 MW of consumption thus affecting large parts of Oslo. Since 1990 the electricity consumption has increased with more than 30 percent, and it is expected to further increase in accordance with population growth and new consumption patterns.

- To ensure the power supply in Greater Oslo in the years to come, it is important to renew this interconnection. This must happen regardless of how much the consumption of electricity increases. Renewing the main grid in Greater Oslo is necessary to meet the demands for supply security, urban development and electrification of Oslo, says Vardheim.

Cables in tunnel
The permit from NVE allows Statnett to make a tunnel from Sogn to Ulven substations for the new cables.

- Cables in tunnel are less exposed to injury, they are easier to inspect, maintenance is easier, they affect the surroundings less, are more economic and require a shorter construction period than cables in trench. The tunnel is also an investment in future upgrades, as that will be a lot easier with a tunnel, says Jan Nyborg, newly appointed project manager for the Sogn-Ulven tunnel project.

The renewal is step two of the upgrades of the main grid in the Oslo area. The first step was renewing Smestad and Sogn substations, as well as the interconnection between these. The new cables between Smestad and Sogn will also be in a tunnel, and the planning work is well underway.

Investment decision and further planning
The Board of Directors of Statnett made the decision to invest in the Sogn-Ulven project May 16th, 2019.

- The project has with this decision reached an important milestone. We will now continue with the detail planning of the new interconnector. We will develop a plan in which we establish what environmental considerations we will take, plans for construction traffic and set the rules for the construction sites. When making these plans, we wish to initiate an open and constructive dialog with all affected parties. We will also start negotiation and signing contracts with the entrepreneurs, says Nyborg.

Register your energy well
The construction of the tunnel may affect residents with a ground source heat pump, living above the tunnel.

- Statnett wants to know about all the ground source heat pumps in the area that has not already been registered, so we can make a technical evaluation of how they will be affected. We will also be able to see if any measures need to be made, says project manager Nyborg.

If you have not already registered your well, you can do so here (LINK).

You can read the full permit from NVE here (LINK).

The decision made by NVE can be appealed. The deadline for appeals is xxxx.

Facts about the project:

The existing cables are owned by Hafslund. The new cables will be owned by Statnett.

Length: ca. 6 kilometers

Number of cables: 2 cable set, each containing 3 cables

Voltage level: 420 kV

Minimum transmission capacity: 2500 MW in total. This is the equivalent of 2,5 million heaters being turned to 1000 W at the same time.

Cable type: PEX (insulated by plastic)

Planned completion: Five years after final permission

Estimated cost: 1240-1430 MNOK