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Maintaining aging equipment is essential for ensuring the reliability and performance of power substations, which are critical components of electric power systems. Preventive maintenance (PM) policies are widely used in this context, but their definition is often based on fixed schedules that do not explicitly account for system degradation and failure dynamics. This paper proposes a structured decision-making framework for evaluating the extension of PM intervals in complex engineering systems. The approach integrates Reliability Block Diagram (RBD) modeling with an imperfect maintenance representation based on the Generalized Renewal Process (GRP) and a Kijima model, allowing the representation of cumulative degradation effects. A decision criterion combining system reliability and the expected number of failures is defined to assess the feasibility of maintenance strategies. The framework is applied to a power substation case study, with emphasis on the transmission line subsystem, considering different PM extension scenarios and parameter uncertainty through sensitivity analysis. The results show that maintenance interval extension must be treated as a constrained problem, in which reductions in maintenance effort must be balanced against increased degradation and failure risk. For the presented case study, only moderate extensions are found to be consistently feasible across all evaluated conditions. The proposed approach provides a systematic and practical method for supporting maintenance planning under uncertainty, enabling consistent and transparent evaluation of maintenance strategies.
Murad et al. (Thu,) studied this question.