Electrical Substation Efficient Maintenance Policies Based On Semi-Markov Modeling and Approximate Inverse Preconditioning

Maintenance is one of the most critical tasks during the operation of a system. The reason is profound as it has effect on the life extension of its components and provides also a better delivered quality of service. Thus a maintenance policy may increase the reliability, the availability and other performance indicators which are mainly used to measure maintenance efficiency, but it also increases significantly the operational cost of the whole system. This fact has raised the need for an optimal of a maintenance policy. This means that the selected maintenance policy must maximize the reliability for a given operational cost, or to minimize the operational cost of the system under some constraints, like keeping the reliability indicator above a threshold point. Maintenance optimization has been extensively studied over the last fifty and either operation research methods were applied to the preventive maintenance or Reliability Centred Maintenance was adopted for maintenance scheduling of electric power networks. But although Reliability Centred Maintenance is a cost effective method for selecting a maintenance policy, unexpected failures still occur which share two characteristics, their cause is random and their frequency is rather sparse. In this case corrective maintenance seems the only way to handle them. In this paper an electrical substation with two power cables and two transformers is modeled in order to determine its overall cost performance due to maintenance activities and components failure. The main aim is to distinguish an effective trade off between preventive and corrective maintenance. The system is modeled under two different scenarios according to types of failures that can occur, in order to trace possible changes in cost’s behaviour and find its impact on determining an efficient maintenance policy. A Semi-Markov Process is adopted in order to model the system as some of the times needed to transit from a system state to another, are not exponentially distributed. More precisely, the Electrical Substation Efficient Maintenance Policies Based On Semi-Markov Modeling and Approximate Inverse Preconditioning J.B. VIOLENTIS, A.N. PLATIS, G.A. GRAVVANIS, V.P. KOUTRAS Department of Financial and Management Engineering, Business School, University of the Aegean, 31, Fostini street, GR 82100 Chios, Greece; Email: [email protected]; [email protected]; [email protected] 2 Department of Electrical and Computer Engineering, School of Engineering, Democritus University of Thrace, 12, Vas. Sofias street, GR 67100 Xanthi, Greece; Email: [email protected]