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Case study

Entr assesses HVDC platform solutions for hybrid grid connections

Entr was commissioned by Statnett to conduct a study to screen possible design solutions for a HVDC platform for the potential realization of hybrid grid connection in the Southern North Sea.

Sørlige Nordsjø II development field
North Sea
October 2023 - March 2024
The challenge

The Norwegian Ministry of Energy stated that for the 2025 offshore wind allocation, it may be relevant to investigate hybrid grid solutions in the second phase of the Sørlige Nordsjø II development field. Statnett will be responsible for hybrid solutions in the grid development and was tasked to further investigate different grid options.  

This led to Statnett engaging with Entr to examine how different HVDC configurations, including symmetrical 320 kV monopole and 525 kV bipole platforms can be designed for hybrid connections. The assignment also included assessing design sensitivities around export voltage levels and identifying ways to include a third future connection. 

The scope included:  

  • Technical description, evaluation, and comparison of existing and planned platform solutions for offshore HVDC substations.
  • Technology maturity, TRL level and need for technology development, including optimization, time perspectives and risk.
  • Relationship between factors, drivers and/or technical factors affecting platform design with respect to concept, voltage, capacity (MW), size, weight, price and technology development needs. This included installation, operation and maintenance philosophy, auxiliary systems, as well as sustainability.
  • Assessment of opportunities for AC expansion of HVDC platforms for consumption (oil, gas, hydrogen production, etc.).  
  • Cost estimates for described solutions.
We are very pleased with the report. It gives us a lot of useful information about possible platform solutions and forms a good knowledge base for our further work.
Our solution

Leveraging our vast expertise in offshore wind, marine operations, and electrical transmission, we conducted an in-depth study focusing on technical and weight-optimized design. Our goal was to achieve low CAPEX and OPEX costs and enable the use of all lifting vessels for the customer.


The collaboration resulted in a detailed comparative analysis of HVDC hybrid configurations, including symmetrical 320 kV monopole and 525 kV bipole platform designs. Our findings provided Statnett with valuable insights into new and previously untested technologies. The study was completed on time and the result met the customer's requirements.  

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