A STUDY OF THE FAILURE AND REPAIR RATE INDICATORS OF THE ITAIPU GENERATOR UNITS

摘要

This paper presents the development of a six states probabilistic model for the Itaipu generating units, focusing on possible state space. This model is defined by the possible states of the equipment and the transition rates between these states and will contain the operating and failure states and the transition rates between them: the failure rate and the repair rate. In addition to these rates, the rate of unavailability and the mean times associated with these states was also calculated to study the evolution of scheduled maintenance as time passes and their importance in the rate of unavailability. It is adopted the alignment by the start operation for the methodology of determination of the proximity of temporal models of failure rate and also of the unavailability rate, as well as for the average time of repair due to failures. So, the operating time used for the failure rate is not the chronological date of start of operation. In addition, the optimum size for the sliding window for calculation of the failure rate curve was analyzed, which reproduces as accurately as possible the characteristics of the bathtub curve for the generating units, four window widths were tested and a criteria to decision is proposed. The fundamental point for applying the methodology and to obtain the rates is the existence of the historical state data from the twenty units of Itaipu power plant in 33 years of operation. The paper yet analyze separately the two generating units that were put into operation between 2006 and 2007, since the first 18 units went into operation during the 1980s and 1990s, and it became evident that the generating units distinguish between them in terms of operating time. The results obtained were satisfactory for the complete representation of the state space and its transitions and for the temporal behavior of these rates. In addition, it was possible to observe some aspects related to the performance of the maintenance policy adopted over the years of operation.