Power Transformer Risk Management based on Reliability Targets

Rabah Medjoudj, Nadir Tighidet, and Djamil Aissani


Power transformer, Reliability, Availability, Preventive maintenance, Markov model, Weibull-Markov model


The aim of this paper is the study of the improvement of maintenance to reliability using two factors. The selection of the action to do on the components on every preventive maintenance stage is decided regarding the required reliability level achievement and by maximizing system benefit on maintenance. The risk management is directly related to the reliability threshold values interpreting customer’s requirements. It is demonstrated that it is possible to provide several reliability levels depending on the customers’ wants and their costs. The implementation of models is done on a real case study and concerns the MV/LV power transformer installed in urban distribution system. The life cycle of the item is modelled using a three states diagram. The transition probabilities between states are based on Weibull distribution functions. These two proprieties led to the consideration of the Weibull-Markov approach. It is proved that it is possible to maintain in another way than the classical one based on systematic preventive maintenance and that policy is conducted on reliability level and benefit bases.

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