Reliability Analysis and Maintenance Optimization of Protective Relays Using an Improved Markov Model

Routine tests in a preventive maintenance plan detect hidden failures and prevent mal-functions. The use of probabilistic models based on Markov chains is conventional in the reliability studies. The well-known models include both states of power system and protection system. This technique increases the complexity of model and study. In this letter, a state-of-the-art Markov model for analysis of the protective relays' reliability is assessed and an improved model is proposed. The power system states are removed from the model and instead the interactions of two systems are considered in the transition rates and costs. The proposed probabilistic model of numerical relays is used to optimize the cost of maintenance considering the back-up protection and uncertainties.