An innovative subsea cable

TENNET DEVELOPS NEW CABLE WITH SUPPLIERS

40% OF THE DUTCH ELECTRICITY WILL COME FROM OFFSHORE WINDFARMS BY 2030. TENNET WILL REALISE THE GRID CONNECTIONS FOR THESE WINDFARMS. ALONGSIDE THE EIGHT 0.7GW AC GRID CONNECTIONS ALREADY PLANNED, TWO 2GW OFFSHORE GRID CONNECTIONS WILL BE built in the IJmuiden Ver wind energy area. Three additional 2GW offshore grid connections in the LanWin and Balwin area will lift TenneT’s offshore grid connection capacity in Germany to more than 17GW until 2030.

ALL IMAGES COURTESY OF TENNET. A 2GW offshore grid connection is currently non-existent. Innovation is needed and TenneT invited eight cable suppliers to develop these ‘next level’ subsea cable systems. This new cable system will set a new standard for connecting offshore windfarms. A 525kV HVDC extruded submarine cable system with a 2GW capacity is currently not implemented in any project worldwide. The development programme should result in a certified cable system that TenneT can apply in the IJmuiden Ver, BalWin and LanWin projects, as well as projects using the same power output and voltage. This will reduce costs and minimise spatial impact.

Besides reducing installation costs, the new subsea cable system is also expected to reduce dredging costs because all cables can be put in a single trench.

New standard in submarine cable systems The eight contractors are Hellenic Cables, LS Cable & System, Nexans Norway, Ningbo Orient Wires & Cables, NKT HV Cables, Prysmian Powerlink, Sumitomo Electric Industries, and Zhongtian Technology Submarine Cable. “It is very positive to see that multiple international cable suppliers are participating in this programme. It shows that the sector is keen to innovate together to produce a new standard for submarine cable systems, substantially reducing cost for society”, says Marco Kuijpers, Director Offshore Projects at TenneT.

Development programme To link 2GW offshore grid connections to the onshore grid system requires a suitable (new) certified cable system. This cable system will connect a 2GW platform and a land station. To transport the required 2GW power, a subsea cable system operating at a voltage level 525kV DC using extruded insulation types is needed. All participating cable suppliers will develop and test the cable system within the time frame for the 2GW projects and TenneT will be in close contact with them during the entire process. TenneT expects that the development of the 525kV DC submarine cable system will result in a certified system in Spring 2022. Following this path, the development programme enables both developers and TenneT to deliver a new cable system costefficiently and in time. Less impact The need to develop this subsea cable system is derived from the expectation that it will reduce manufacturing and installation costs. Not only for the cable system itself but for the entire grid concept, including the High Voltage Direct Current (HVDC) offshore platform and the HVDC land station. TenneT expects the bundled installation to achieve significant cost reductions. Besides reducing installation costs, it is also expected to reduce dredging costs because all cables can be put in a single trench. This approach also results in fewer platforms and land stations, which is not only interesting in financial terms but also ensures that TenneT causes lower emissions and has less spatial and environmental impact.

Next step in energy transition TenneT is constantly seeking to take steps in the energy transition that can contribute to the offshore targets of safely and costeffectively transporting offshore windfarms. Given the increase in size of the IJmuiden Ver windfarm and the distance to the nearest connection point, it was decided to apply the ‘new’ 525kV 2GW grid concept. This is a logical move after installing eight standard AC connections in capacity of 700MW, bringing the total installed capacity offshore wind connected by TenneT to 9.6GW in the Netherlands alone in 2030.

i. tennet.eu

A 2GW offshore grid connection is currently non-existent. Innovation is needed and TenneT invited eight cable suppliers to develop these ‘next level’ subsea cable systems.