Optimal maintenance scheduling in a parallel redundant system consisting of series components in each branch

A set of equations is developed in this paper and used in conjunction with the minimal cut set method to evaluate the total failure frequency of a parallel redundant system consisting of series components in each branch where each component can operate in its wearout period and the failure rate of each component is not constant. The optimum maintenance intervals are determined based on the criterion that the total failure frequency of the system is minimized. The Newton-Raphson method is applied to obtain the unknown optimum maintenance intervals for the system. The proposed approach is presented and illustrated using a practical substation example.