The protection of DC systems in mobility applications, such as land transport, aircraft, and shipping, presents significant challenges due to the need for high power density equipment in confined spaces. This paper focuses on DC systems on board ships, for which diverse applications require different power levels, architectures, and protection strategies. Existing protection frameworks and regulations are often inadequate or outdated for the field, leading to certification issues and insufficient fault analysis. This research proposes a use case-based categorization of short circuit currents for primary systems. A reference scenario is created using a simulation model of a 5 MW system in a superyacht to provide a short circuit inventory. The study proposes three contributions. A comprehensive fault inventory, a qualitative categorization, and relevant recommendations for power converter design. The research highlights the importance of fault categorization in understanding the impact of various short circuits on shipboard DC systems. The study emphasizes the importance of the evolution of materials and power converters in developing efficient protection technologies for ships. This work addresses some fundamental gaps in shipboard DC systems, providing a foundation for improved protection strategies and regulations, ultimately contributing to the advancement of protection of shipboard DC systems.