Using system-theoretic process analysis and event tree analysis for creation of a fault tree of blackout in the diesel-electric propulsion system of a cruise ship

Diesel-Electric Propulsion (DEP) has been widely used for propulsion of LNG carriers, icebreakers, drilling units, warships and cruise ships. It is important that every blackout is prevented, especially on cruise ships, considering the possible consequences of such an event. In this work, hazard analysis of a simplified DEP system of a cruise ship is implemented to identify the hazardous scenarios leading to a blackout. This is achieved by combining System-Theoretic Process Analysis (STPA) and Event Tree Analysis (ETA). The STPA is used to identify the hazards and the possible control actions leading to hazards along with their causal factors, whilst the ETA is used to determine the propagation of hazards into the other hazards or accident. Next, the results of STPA and ETA are mapped into a Fault Tree for better representation of results. In this way, the relationship between accident, hazards and unsafe control actions is explicitly described and a more comprehensive picture of the potential accidental scenarios in the system is provided, rendering possible allocation of quantitative performance requirements as per IEC 61508.