Unreliability tracing technique for system components based on the fault tree analysis

A new method is developed for tracing the unreliability contributions of system components and recognizing the system weak parts using the fault tree analysis (FTA). The method is based on the minimum cut set (MCS) algorithm for evaluating the system reliability using the FTA and the proportional sharing principle (PSP). The fault tree can be expressed as MCSs and the system unreliability can be mathematically expressed by a certain terms of probability of occurrence of MCSs. A unreliability tracing (UT) principle is proposed for allocating the probability of each term to the basic events fairly and reasonably, and then the direct contribution relationship between the system unreliability and basic events can be established. The system UT sharing factors (UTSFs) are derived to easily identify the weakness parts in a system. The applicability of the proposed methods is illustrated by case studies of a simple system and a multiple-output power distribution system.