Dynamic System Reliability

6Deterministic Common‐Cause Failure

According to [1], common‐cause failures (CCFs) are “A subset of dependent events in which two or more component fault states exist at the same time, or in a short time interval, and are direct results of a shared cause.” There are two types of shared root causes or common causes (CCs): external causes and internal causes. Examples of external causes include floods, lightning strikes, earthquakes, sudden changes in environments, malicious attacks, design mistakes, power‐supply disturbances, human errors, radiations, computer viruses, etc. Internal causes are mainly propagated failures (PFs) or destructive effects like fire, overheating, short circuit, blackout, or explosions originating from some component within the system, which may destroy or incapacitate other system components.

CCFs typically happen in systems that are designed with redundancy techniques based on the use of s‐identical components [2]. It has been shown by numerous studies that CCFs tend to increase joint component failure probabilities, thus contributing significantly to the overall system unreliability [3–14]. For example, according to studies performed by Fleming et al. [14] , the unreliability of a system with CCFs can be increased by more than a factor of 10 in varying CCs contribution up to 1%. In other words, failure to consider CCFs can lead to overestimated system reliability metrics [12,13]. Therefore, it is crucial to incorporate effects of CCFs for the accurate ...