Øresund 400kV

Energinet Eltransmission A/S concluded a works contract titled "400 kV offshore installation for Øresund 2" with JD Contractor A/S on 11 September 2024 for installation of a reinvestment 400 kV cable system of three single-core cables between the transition stations Skibstrupgaard (SKB) in Denmark and Kristinelund (KLD) in Sweden. The award is recorded in EU contract award notice 587834-2024 (OJ S 191/2024) for the lot covering offshore installation and associated works.

In June 2024, Energinet launched a procurement process seeking civil and cable works for the Øresund 2 400 kV system project, covering pipe installation, underdrilling and removals as part of the Øresund 400 kV interconnector replacement works.

Hellenic Cables signed a contract with Danish TSO Energinet to supply the 400 kV AC interconnection cable system between Denmark and Sweden, part of the Øresund 400 kV link. Under the agreement, Hellenic Cables will design, manufacture and deliver about 30 km of submarine and 12 km of underground single‑core 400 kV cables, and will supervise installation, testing, jointing and termination, with production starting in 2023 and deliveries expected in the first half of 2024.

By late November 2023, Svenska kraftnät had commenced soil sampling (markprovtagning) within the Domsten–Viken nature reserve as part of onshore geotechnical investigations ahead of the planned renewal of the northern Öresund 400 kV cable connection. The works required closure of the public parking area during week 48 and, due to delays, this closure was extended through weeks 50 and 51 in December 2023.

The Danish Ministry of Climate, Energy and Supply approved Energinet’s application to replace System 2 of the 400 kV submarine cable connection across the Øresund strait between Denmark and Sweden, allowing Energinet to begin the project to renew the ageing cable that links Zealand with southern Sweden. The approval covers the replacement of the existing 37‑year‑old cable and underpins a DKK 486 million (€65.2 million) project that is described as central to the operation of the Eastern Danish electricity system and to maintaining synchronous operation with the Nordic region.

On 3 October 2022, Svenska kraftnät announced that it was inviting stakeholders to a statutory consultation (samråd enligt 6 kap. miljöbalken) for the renewal of the northern 400 kV cable connection between Grå Läge in Helsingborg, Skåne, and Själland in Denmark, giving property owners, authorities, municipalities, the county administrative board, interest organisations, and the general public the opportunity to submit comments on the project.

Energinet initiated feasibility studies in the summer of 2022 for the replacement of System 2 of the 400 kV cable connection across the Øresund, part of the Øresund connection linking Zealand in Denmark with southern Sweden. These studies support the project to replace the ageing, 37‑year‑old submarine cable owned by Energinet and prepare for installing new onshore and submarine cables between the Skibstrupgård and Kristinelund transformer stations.

By 2020, the Öresund 400 kV HVAC cable replacement project for Svenska kraftnät had been executed, with four new 7.3 km power cables installed between Denmark and Sweden, including piggybacked fibre‑optic cables and 1,800 m of additional cable protection, all carried out within a tightly restricted 35‑day outage window in the Øresund Strait.

SCOPE: This decommissioning event applies ONLY to System 1 of the Oresund 400 kV interconnector — the original 1973-installed oil-filled southern cables. By 2020, decommissioning of the four old oil-filled 400 kV power cables on the System 1 circuit between Kristinelund (Sweden) and Skibstrupgaard (Denmark) was completed, with VBNK finishing their removal as part of a 2019-2020 project scope that cleared the way for installation of four new replacement cables on this circuit. This event does NOT indicate decommissioning of the whole Oresund 400 kV project — System 1 was immediately replaced with new cables (see replacement_cable_installation_complete 2020) and has been operational since 2020. System 2 (the northern circuit, original 1985 cables) continues to operate in reduced-capacity mode pending its own replacement campaign (2025-2026, Energinet with Hellenic Cables supply + JD Contractor installation, COD projected December 2026). The project-level status is part_operational: one of the two parallel systems is fully operational while the other is in active replacement construction.

First power transmitted on the new System 1 (southern circuit) of the Øresund 400 kV interconnector after the 2019-2020 replacement of the original 1973 oil-filled cables. NKT's reference page for the Upgrade of the Øresund connection between Sweden and Denmark states that NKT completed "testing, commissioning and energizing" of the approximately 9 km 400 kV HVAC offshore and onshore cable system within the project's 2019-2020 schedule, confirming that the new System 1 cables reached first power and returned the southern circuit to full operational service by end of 2020. Year precision used because NKT's reference does not give a specific commissioning day; the 2020 window is however firmly bounded by the decommissioning_complete event (also 2020) and the 35-day outage constraint applied by Svenska kraftnät to the Øresund Strait. This event is distinct from first_power of a newly built project — it marks the return to service of the replacement System 1 cables on a pre-existing interconnector that had been in service continuously on the System 2 circuit. Recorded during manual audit review 2026-04-15 to make the status_derivation correctly reflect that the project is part_operational (System 1 fully operational, System 2 being replaced 2025-2026 with Hellenic Cables + JD Contractor, COD projected December 2026).

In March 2020, Elnos Group commenced onshore construction works on two 400 kV overhead transmission line sections (FL 25 and FL 23) near Helsingborg, Sweden, dismantling old towers and conductors, erecting new towers, and installing new conductors, protective ropes and OPGW as part of Svenska kraftnät’s project to renew the Öresund 400 kV cable and associated transmission infrastructure, which was completed in 2020 for System 1.

For the Upgrade of the Öresund connection between Sweden and Denmark, NKT completed testing, commissioning and energizing of the around 9 km 400 kV HVAC offshore and onshore cable system within the project’s 2019–2020 schedule, confirming that system testing and commissioning of the replacement cables were finished by 2020.

Energinet reports that the Øresund 400 kV System 2 cable connection between Zealand and southern Sweden was damaged in 2019, an event that reduced the capacity of the interconnector and led to socio‑economic losses due to the constrained transmission capability.

In 2019, decommissioning of the ageing southern 400 kV oil-filled HVAC cables in the Øresund connection between Kristinelund in Sweden and Skibstrupgaard in Denmark began, with contractor consortium VBNK (Boskalis and NKT) starting removal of four existing cables that had reached the end of their technical lifetime as part of a replacement project.

On 12 November 2018, a consortium of NKT and Boskalis was awarded a turn-key contract to replace the Øresund 400 kV high-voltage AC interconnector system between Denmark and Sweden, covering the design, production and installation of four new 400 kV power cables and the removal of the original 1973-installed cables. The project, ordered by Swedish TSO Svenska kraftnät for the Øresund sea crossing, has an order value of approximately €22 million for NKT and aims to maintain secure power transmission between the two countries.

An April 15, 2014 article in Ocean News & Technology reports that MMT was awarded a contract by Svenska kraftnät to perform a marine cable route survey for the 400 kV AC Själland cable system across the Öresund between Denmark and Sweden, including geophysical and geotechnical investigations. The article states that offshore operations will start in spring 2014. Given this, it is reasonable to place the geophysical survey start in mid‑April 2014, aligning with the contract announcement and stated spring start.

Energinet has submitted an application for an environmental impact assessment (EIA) permit to the Danish Environmental Protection Agency for the Øresund System 2 400 kV cable replacement project, covering the submarine cable across Øresund between Skibstrupgaard in Denmark and Kristinelund in Sweden. This submission initiates the formal environmental permitting process for the Danish part of the interconnector replacement.

On the 8th of January (year not specified), one of the 400 kV Øresund interconnector cables between Denmark and Sweden was taken out of service after Energinet detected an oil leak from the 35‑year‑old oil‑filled cable, removing the circuit from operation to protect the marine environment.

Following the outage on one of the 400 kV Øresund cables, Energinet activated its contingency framework with JD‑Contractor, which rapidly mobilised several vessels including diving ships Cable One and Honte and the cable repair barge Henry P Lading, freed several kilometres of buried cable, repeatedly lifted and partially froze the cable to locate the leak 1.32 km from the Danish coast at about 26 m water depth, and carried out the repair, which passed a 24‑hour soak test before the cable was re‑embedded.

After JD‑Contractor completed the repair and a successful 24‑hour soak test on the damaged 400 kV Øresund cable, the re‑embedding of the cable was finished on 22 February (year not specified), allowing Energinet to return the interconnector circuit to operation.

As part of the Öresund 400 kV energy link reconstruction, Elnos Group undertook major works on two overhead transmission line sections FL 25 and FL 23 near Helsingborg, dismantling old towers and conductors on the route to substation Kristinelund, erecting new towers, installing new conductors, protective ropes and OPGW, with work that started in March and was scheduled to be completed by 1 June under investor Svenska kraftnät.

For Energinet’s planned replacement of the existing 400 kV cable system across the Øresund, Deep’s surveying team, working with Ramboll, completed a marine route survey along the cable corridor. Using the vessel Deep Seapal equipped with dual‑head multibeam echo‑sounder, side‑scan sonar and magnetometer, they collected seabed and sub‑seabed data over a 16‑day campaign and delivered processed results and interpretations to Energinet.

As part of Energinet’s Øresund 400 kV cable replacement preparations, Deep carried out UXO detection and avoidance surveys along the planned cable route in the Øresund Strait. These UXO surveys were delivered together with marine geophysical, hydrographic and cable‑route investigations, and the resulting processed data package was provided to the client to inform safe routing and installation of the new 400 kV cables.