Generally, stochastic point processes are employed in reliability analysis of repairable systems. However, when failures and reparations of these systems occur in a non-stationary trend over time, for example due to aging, it is required to use non-homogeneous Poisson process. In this paper, it is presented a general methodology for reliability assessment of repairable systems using non-homogeneous Poisson process. The methodology uses sequential Monte Carlo simulation and is applied to a power distribution test system affected by adverse weather conditions and aging of its components. As a conclusion, it was found non-homogeneous Poisson process is an excellent tool for modeling the reliability of repairable systems when it is required to consider realistic conditions in the analysis.