“…For instance, in [9] the optimal PM problem for substation components is solved by a Monte Carlo simulation technique, but most studies are focused on solving the optimal maintenance problem by particle swarm optimisation (PSO) or genetic algorithm (GA) techniques. For instance, [10] is about the application of PSO for the optimum maintenance in transmission systems and [11] is about finding the optimum scheduling for maintenance period by hybrid scatter-genetic algorithm (HS-GA), while [12] presented a method for reliability centered maintenance (RCM) programs by a multi-objective GA. Several papers presented new methods and models for solving maintenance problem and modelling components condition. For instance, [13] presented a new method named T* strategy to find the optimal maintenance time and [14] presented a new model for reliability analysis.…”