Nexans sets new world record for deepwater HVDC cable technology

Nexans has completed the qualification of a 525 kV HVDC mass impregnated cable system for installation at a record-breaking water depth of 3,000 meters, a world first, presented at CIGRE Paris Session 2026 (23–28 August).

Nexans has reached a major technological milestone: the successful qualification of a 525 kV HVDC mass impregnated (MI) cable system for installation at a record-breaking water depth of 3,000 meters. The achievement sets a new world record for submarine power cable installation depth.

The milestone was achieved as part of the Great Sea Interconnector (GSI) project, which will connect Crete and Cyprus through a ±525 kV HVDC subsea transmission link.

Full system qualified, including the flexible repair joint

Most recently, the project’s flexible repair joint completed its mechanical and electrical type test program, including testing under the extreme mechanical loads associated with installation at 3,000 meters water depth. During mechanical testing, the cable system was subjected to a test tension of up to 842 kN.

This completes an extensive qualification program covering the 525 kV HVDC MI cable, flexible factory joint and flexible repair joint, demonstrating that the complete cable system can withstand the demanding mechanical and electrical conditions associated with ultra-deepwater installation.

From qualification to real deepwater conditions

The achievement builds on another milestone already completed by the project: a full-scale sea trial at 3,000 meters water depth, announced by Nexans in March 2026. During the trial, Nexans installed and recovered the NOVA-L 525 kV 1×1300 mm² aluminum MI cable and joint under real offshore conditions. The cable was subsequently electrically tested and inspected, confirming the robustness of the system after exposure to the deepwater installation process.

Together, the sea trial and the completed type testing provide the technical basis for installing a 525 kV HVDC MI cable system at depths previously beyond the industry’s established limits.

What 3,000 meters changes for power transmission

Reaching 3,000 meters is a substantial extension of the operational envelope for HVDC links, not an incremental step. Many planned long-distance interconnectors and offshore transmission schemes cannot be realized with shallow-water technology alone: in several regions, the shortest, or only, feasible transmission route passes through very deep waters, beyond 2,000 meters and up to 3,000 meters or more. Until now, such routes were often considered too risky, too costly, or infeasible from a cable-system standpoint.

A 525 kV HVDC MI cable system qualified at 3,000 meters expands the geographic options available for power-cable corridors, making previously excluded deep-sea routes viable candidates in techno-economic route planning. New deepwater corridors can shorten interconnection distances, ease routing constraints, and reduce environmental and coastal impact, while supporting more flexible grid architectures.

Presented at CIGRE

Nexans is currently the only manufacturer with a power cable system qualified for installation at 3,000 meters water depth. The milestone is being presented to the international power systems community at CIGRE Paris Session 2026, running from 23 to 28 August at the Palais des Congrès, where Nexans is sharing the technology and experience behind this new benchmark for deepwater HVDC cable installation.

At a glance

• Achievement: Full qualification of a 525 kV HVDC mass impregnated (MI) cable system for installation at 3,000 meters water depth
• World first: Nexans is the only manufacturer with a power cable system qualified for installation at this depth
• Project: Great Sea Interconnector (GSI) (Crete–Cyprus)
• Key milestone: Successful qualification of cable, factory joints and repair joints
• Tested load: Up to 842 kN mechanical tension.

Why it matters

• Makes ultra-deepwater power transmission projects possible
• Opens new routing options for future interconnectors
• Supports more resilient and flexible power grids.