Skagerrak 2 HVDC Submarine Cable Fault Reduces Norway-Denmark Power Interconnection by 245 MW

Oslo, Norway — Statnett, Norway’s national grid operator, confirmed that the Skagerrak 2 HVDC submarine interconnector between Norway and Denmark returned to service on 2 September, after nearly three months of unplanned outage triggered by a subsea cable fault discovered on 2 June 2026.

Key Facts at a Glance

The Fault and Its Cause

The fault point was located approximately 30 kilometres off the Danish coastline. Post-fault underwater surveys and seabed inspections ruled out anchor damage, fishing gear impact or sabotage. Operators concluded that the failure stemmed from long-term material ageing and the gradual deterioration of minor pre-existing defects within the cable body. Commissioned in 1977, Skagerrak 2 has operated for close to 50 years.

Impact on Cross-Border Power Transfer

The outage cut the cross-border power transfer capacity by 245 MW. The full Skagerrak interconnection system originally delivers 1,632 MW of bi-directional power flow between the two Nordic nations — capacity that is critical for balancing variable hydro and wind power across the regional electricity market. A loss of this scale underlines how dependent the Nordic grid has become on a small number of high-capacity subsea links.

Repair Work and Return to Service

During the repair window, engineering teams carried out subsea cutting, sealing and jointing work at the fault section. Statnett and the Danish grid operator Energinet stated that this incident highlights the reliability risks facing ageing legacy submarine HVDC assets across Europe. Many cross-border subsea cable links are approaching end-of-life, requiring systematic asset inspection, condition monitoring and renewal planning.

Ageing Subsea Assets: A Growing Reliability Risk

Industry analysts point out that ageing subsea cable failures often lead to multi-month downtime and substantial market volatility. The event reinforces the growing demand for advanced cable fault location technology, regular condition assessment and modern high-performance HVDC submarine cable replacement programmes.

Incidents like the Skagerrak 2 cable failure demonstrate that hidden insulation defects and material ageing in power cables require regular condition monitoring and preventive testing to avoid catastrophic outages. Traditional passive maintenance methods can hardly identify latent cable defects in advance, resulting in long repair cycles and huge economic losses once faults occur.

Professional Cable Testing and Fault Location Solutions

XZH Test offers a full range of professional cable test and fault location instruments for both submarine and underground power cables, enabling power operators, offshore engineering teams and cable contractors to detect early insulation degradation, identify latent ageing defects, and pinpoint cable fault points rapidly.

TDR Cable Fault Locator

High-precision TDR, impulse-current and acoustic-magnetic locators that pinpoint underground and submarine cable faults quickly and accurately.

High Voltage Impulse Generator

Portable surge generators (thumpers) up to 35 kV that break down high-resistance and flashing faults to create a detectable discharge at the fault point.

Cable Fault Pinpointer

Cable fault pinpointing instrument; precisely locates cable faults with an error margin of no more than one meter.

Cable Sheath Fault & Route Locator

Sheath fault testers and electromagnetic route/depth locators for locating sheath defects and mapping cable routes before and after installation.

By implementing standardized pre-commissioning tests and regular preventive maintenance with XZH Test equipment, power enterprises can effectively reduce unplanned outage time, extend the service life of power cable assets, and ensure the long-term stable and safe operation of ultra-high-voltage transmission and cross-border grid interconnection projects.