Failure decomposition based on the general time sequences for cold standby systems

Failure sequences are the time relationship of different components failures, and solving the occurrence probabilities of failure sequences is aid for failure path identification. When there are common cause failure (CCF) causes, the failure time sequences of the cold standby system is more complex. For the systems with various failure probability distributions, there are challenges for failure probability solution. This paper proposes a method of general time sequences, realizes the division of failure time sequences, and calculation the occurrence probabilities of time sequences and the system failure probability. Considering that subsequent CCF or other component failures that may occur after the system meets failure conditions, the failure observation time is extended, and the system failure time sequences are categorized according to whether all potential failure causes occur. Further, a constraint analysis method based on changes in states is proposed to solve the occurrence probability of each time sequence and the overall system failure probability. The effectiveness of the proposed method is verified with the Markov models and Monte Carlo simulations, and case studies are carried out with the two-redundancy starter/generator system of the aircraft auxiliary power units and the four-redundancy electrical power supply system. The results show that the proposed method enhances the safety analysis, enriches the theory of failure time sequence, and strengthens the CCF quantitative analysis framework.