Converter transformer in HVDC offshore projects: an approach for risk assessment

This paper proposes a risk analysis framework based on the Monte-Carlo method to assess converter transformer in HVDC projects, with a focus on the importance of short-circuit tests and the optimal sizing of spare parts. The approach evaluates total cost including both CAPEX and the spilled energy in case of outages for different strategies. By simulating thousands of random scenarios, the analysis quantifies the cost-risk trade-offs for each strategy. For example, in the case of three offshore wind HVDC bipole projects, the analysis demonstrates the benefits of performing short-circuit withstand tests. Depending on assumptions and confidence levels, having one or two spare offshore transformers is typically the most cost-effective choice.

Although final recommendations are highly dependent on the economic model and assumptions specific to each project, the methodology provides a robust risk assessment framework that

HVDC project owners can adapt—not just for transformers, but for any key substation equipment. It is also important to note that decision-makers may need to consider non-technical factors in their overall risk management strategies.