TYPES OF MAINTENANCEFour general types of maintenance philosophies can be identified, namelycorrective, preventive, risk-based and condition-based maintenance. In practice, allthese types are used in maintaining power distribution equipment. The challenge isto optimize the balance between the types for maximum plant reliability.1. CorrectivemaintenanceMaintenance is carried out following detection of an anomaly and aimedat restoring normal operating conditions.This approach is based on the firm belief that the costs sustained for downtime andrepair in case of fault are lower than the investment required for a maintenanceprogramme.This strategy may be cost-effective until catastrophic faults occur.2. PreventivemaintenanceMaintenance carried out at predetermined intervals or according to prescribedcriteria, aimed at reducing the failure risk or performance degradation of theequipment.The maintenance cycles are planned according to the need to take the device outof service. Theincidence of operatingfaultsisreduced.3. Risk-basedmaintenance
Maintenance carried out by integrating analysis, measurement and periodictest activities to standard preventive maintenance.The gathered information is viewed in the context of the environmental, operationand process condition of the equipment in the system. The aim is to perform theasset condition and risk assessmentand define the appropriate maintenanceprogram.All equipment displaying abnormal values is refurbished or replaced. In this way itis possible to extend the useful life and guarantee over time high levels ofreliability, safety and efficiency of the plant.4. Condition-basedmaintenanceMaintenance based on the equipment performance monitoring and the control ofthe corrective actions taken as a result.The real actual equipment condition is continuously assessed by the on-linedetection of significant working device parameters and their automatic comparisonwith average values and performance. Maintenance is carried out when certainindicators give the signaling that the equipment is deteriorating and the failureprobability is increasing.This strategy, in the long term, allows reducing drastically the costs associated withmaintenance, thereby minimizing the occurrence of serious faults and optimizingthe available economic resources management.¿which is preventive maintenance?¿which is corrective maintenance?