The degree of complexity of the Integrated Power Systems (IPS) for All Electric Ships (AESs) promotes the need to review the design process from a dependability perspective. This paper suggests the application of dependability concepts and definitions to demonstrate adherence to requirements set forth by recent rules and regulations as regards to threat levels for shipboard electrical equipment.
Guidelines on 1) how to properly decompose the IPS into conceptual subsystems; 2) how to define appropriate mathematical models suitable to investigate such sub-systems in a quantitative fashion using RBD (Reliability Block Diagram) and DRBD (Dynamic Reliability Block Diagram); 3) how to define the threat level the IPS (or the sub-system object of the study) should be tested against to prove its dependability are given.
Such guidelines and investigation methods will be then applied on a part IPS of a recently built cruise vessel IPS, to illustrate their application to a real case study. A small sub-system will be decomposed according to guidelines, down to a level matching typical ship design practice, defining entities here called “atoms”. A model, showing interactions among atoms, will be prepared applying the RBD and DRBD techniques. Threats and associated performance levels will be derived from relevant international rules and regulations in force, and “translated” into operations with atoms and “propagation path lengths” within the model; acceptance criteria will, in this framework, be rendered as accept/reject conditions. Considerations regarding the adopted decomposition and applied techniques will be given in the conclusions.
