IN Brief:
- IJmuiden Ver Gamma is the second of three standardised 2GW offshore converter-platform jackets being fabricated in Vlissingen.
- The completed jacket is scheduled for barge transport to an installation point roughly 80km offshore in summer 2028.
- Gamma, Beta and Nederwiek 2 together form 6GW of planned North Sea transmission capacity using 525kV HVDC export systems.
TenneT has started fabrication of the jacket for its IJmuiden Ver Gamma offshore converter platform, with the first steel cut completed at Heerema Fabrication Group’s yard in Vlissingen.
The structure is the second of three standardised jackets being built at the Dutch yard for TenneT’s 2GW offshore grid programme. Heerema is fabricating jackets for IJmuiden Ver Beta, IJmuiden Ver Gamma and Nederwiek 2 under the wider delivery arrangement led by the GE Vernova-Seatrium consortium.
Fabrication of Gamma is expected to run for roughly two years. Large steel sections will be assembled, welded and protected with coatings before being joined into the completed substructure. The jacket is scheduled to leave Vlissingen in summer 2028, travelling by barge to an offshore installation site around 80km from IJmuiden before being placed and anchored on the seabed.
The jacket sits at the start of a long physical delivery chain for the offshore converter platform. The foundation has to be fabricated, transported and installed to the tolerances required for the topside structure, while marine logistics, heavy lifting and the platform construction programme remain aligned.
IJmuiden Ver Gamma follows the same standardised 2GW concept being used for Beta and Nederwiek 2. TenneT’s approach reuses design work, construction methods and project experience across multiple connections rather than treating each offshore converter platform as an entirely bespoke engineering programme.
That repetition is already visible in the yard sequence. Fabrication of the IJmuiden Ver Beta jacket began in September 2025, approximately a year before Gamma. Gamma is now following through the same broad production path, while Nederwiek 2 will form the third jacket in the series. The staggered programme allows different structures to occupy different fabrication stages in parallel as the yard builds experience with the common design.
Together, the three grid connections represent 6GW of transmission capacity for North Sea offshore wind. At each offshore converter platform, alternating current collected from the wind farms will be converted to high-voltage direct current at 525kV for transmission to shore. The power will then be converted back to alternating current at the Maasvlakte before entering the Dutch high-voltage system through the new 380kV Amaliahaven substation.
The move to 2GW connections increases the amount of offshore generation that can be carried by a single transmission system compared with earlier 700MW Dutch offshore links. It also concentrates more capacity into each converter platform, export route and associated onshore station, increasing the consequences of equipment reliability, interface control and programme delays.
Standardisation reduces repeated engineering work but does not remove project complexity. A jacket of this class still has to accommodate large structural loads, North Sea environmental conditions, installation loads and the interfaces required by a converter topside containing heavy electrical equipment. Weld quality, dimensional control, corrosion protection and fabrication sequencing all feed into the later offshore installation campaign.
The converter platform adds another layer of engineering. High-power HVDC equipment must convert and control several gigawatts while maintaining voltage, power quality and system stability across an offshore network exposed to changing wind generation. Protection, auxiliary supplies, cooling, communications and offshore maintenance access have to function alongside the principal converter equipment throughout the asset’s operating life.
The 525kV direct-current export system reflects the distances and capacities involved. For large offshore wind zones tens of kilometres from shore, HVDC reduces the transmission losses and reactive-power issues that become increasingly difficult to manage with long high-capacity AC cable routes. Converter stations add cost and complexity, but they make bulk offshore transmission practicable at the scale planned for IJmuiden Ver.
The three-jacket programme also turns standardisation into a manufacturing exercise. Repeating a common design allows Heerema to carry tooling, work instructions, welding procedures, quality controls and lessons from Beta into Gamma and then Nederwiek 2. Each structure still has to pass its own inspection and acceptance process, but repeated production can reduce avoidable variation between projects.
Offshore grid expansion depends on fabrication capacity beyond cable manufacture alone. Steel structures, converter equipment, transformers, switchgear, specialised vessels, heavy-lift capability and port infrastructure all have to be available in compatible windows. A delay in one package can move marine installation dates and affect topside installation, cable connection, testing and energisation further down the programme.
Gamma’s first steel cut moves another 2GW connection into physical manufacture. The next delivery test is the Vlissingen production sequence, with Beta progressing ahead of Gamma and Nederwiek 2 following through the same yard while Gamma remains scheduled for offshore installation in summer 2028.
