The global expansion of offshore wind energy is accelerating, driven by growing demand for clean electricity and continuous innovation. As projects scale up and move farther from shore, cost-efficient transmission becomes increasingly important. Transmission infrastructure (such as offshore substations (OSS) and export cables) can account for up to 30% of a wind farm’s total capital expenditure, making transmission system design a critical factor for overall project viability.

Recent advancements have enabled offshore wind turbines to generate electricity at 132 kV. This raises a fundamental design question: if turbines are increasingly becoming capable of generating at 132 kV voltage level, does it remain necessary to add costly offshore substations to further step up the voltage or can 132 kV also be used as the export voltage directly to shore? Traditionally, an OSS collects the power from turbines and steps up the voltage for efficient transmission. This thesis explores whether direct-to-shore configurations using 132 kV can offer a technically and economically viable alternative to conventional step-up systems.
While 132 kV systems are beginning to appear in planned projects, existing literature still treats this voltage primarily as suitable for infield collection, not export. The idea that it could also enable direct-to-shore export is rarely discussed and lacks supporting technical or economic analysis, likely due to the novelty of the technology. As a result, the potential to eliminate the OSS (one of the most expensive and complex components in offshore transmission) has not been critically examined.

This thesis addresses that gap by evaluating four transmission configurations - two with offshore substations and two direct-to-shore - within the context of Vattenfall’s 1.2 GW Kattegat Syd project in Sweden. The assessment considered seven key criteria: Capital Expenditure (CAPEX), Operational Expenditure (OPEX), Revenue, Risk, Ease of Implementation, Environmental & Permitting Impact, and Innovation & Scalability.

The 132 kV direct-to-shore configuration outperforms OSS-based systems on CAPEX, Revenue, Risk, and Innovation & Scalability, primarily due to reduced infrastructure and simplified supply chains. In contrast, it performs worse on Ease of Implementation and Environmental & Permitting Impact, due to the immaturity of the concept and the higher number of export cables required, which complicate permitting procedures. This reveals that the main trade-off lies between economic and future-readiness benefits on the one hand, and implementation and permitting challenges on the other.

To incorporate stakeholder preferences into the evaluation, Vattenfall’s Technical Project Manager (TPM) and Project Director (PD) for the Kattegat Syd project were interviewed. Using the Best-Worst Tradeoff (BWT) method, they assigned relative importance to each criterion based on their expertise and project experience. Combining these weightings with the performance scores of each alternative, the 132 kV direct-to-shore option emerged as the top-ranked configuration for both decision-makers.

This thesis contributes scientifically by addressing a clear knowledge gap: although 132 kV turbines are emerging, their use for direct-to-shore transmission has not yet been technically or economically evaluated in academic literature. In addition, the study introduces a previously undocumented system configuration (a 132 kV direct-to-shore setup with an onshore substation near landfall) and demonstrates the practical value of the BWT method as a decision-support tool for complex infrastructure design. The study provides a structured framework for decision-making in offshore transmission planning and sparks the discussion on considering 132 kV direct-to-shore configurations as a viable alternative in future projects.