A Study of the Effect of Basic Network Characteristics on System-of-System Failure Propagation

Real life examples of large system level failures in complex networked system are fairly common, with national and regional level power grids providing numerous cases where local failures have resulted in broad systemic failures. As large networked systems-of-systems are increasingly common, their susceptibility to large scale failures is of significant interest. This paper presents the results of a study using a simple model to investigate the impacts of basic architecture characteristics on the spread of failures through a system-of-system after an initial failure occurs.The study reported here uses a non-symmetric inter-grid only failure model to investigate the sensitivity of failure progression due to failure in dependent nodes in a system-of-system composed of dependent grid networks to the several basic parameters, including initial failure size, grid node density and grid interdependency radius.Despite the use of only an inter-grid failure mechanism, the study results generally showed a rapid failure propagation to a steady state condition. A possible mechanism for this return to steady state in terms of the expanding failure front and probability that existing dependent nodes lie outside of the failure front is discussed