A new reliability model for power system components characterized by dynamic stress and strength

The paper discusses a new reliability model for power system devices for which a physical ageing model may be inferred by describing the wear caused by random stresses. The device reliability function is expressed as the probability that the total wear (stress) accumulated during a given interval is smaller than the electric endurance (strength) and is based upon a "dynamic" version of a "stress-strength" model already developed by the authors in previous papers. The wear is modeled as a succession of "shocks", driven by a Poisson process. The properties of such model are illustrated by means of numerical and graphical examples, showing that it possesses a decreasing hazard rate for large values of service times, as more popular models (e.g. the Lognormal one). Finally, some useful hints for the simulation and the statistical fitting of the model are given