An optimal condition-based maintenance policy for offshore wind turbine blades subject to degradation and shocks
Résumé
In this paper, we investigate an optimal condition-based maintenance policy for a deteriorating“multi-bladed” wind turbine system subject to stress corrosion cracking (SCC) and external shocks. Whenthe length of a crack in a blade reaches a critical size D, the blade fractures and it has to be replaced by a newone. An external shock is minor with probability 1- p and catastrophic (major) with probability p (0 <= p <=1). In order to avoid such costly failures, once the length of a crack in one of the blades exceeds athreshold d ( < D), it undergoes a major repair and a preventive maintenance (PM) action is performed on theother blade(s) as well; otherwise, a planned PM task is conducted on the whole system when its operationalage attains a value of T (> 0). An optimization model is proposed to simultaneously determine the optimalcontrol parameters d* and T* such that the average long-run maintenance cost per blade per unit time isminimized.