Combined-Cycle Power Plant Maintenance Costs

Abstract

This paper describes a methodology to quantify scheduled and unscheduled maintenance costs and a software framework for estimating operations and maintenance (O&M) costs of combined-cycle power plants over their operating life. Scheduled maintenance costs consist primarily of replacement and repair of hot section components of the combustion turbine that occur during planned inspections and overhaul events. Scheduled maintenance costs can be estimated based on anticipated parts life, operating conditions and parts costs. Some degree of uncertainty exists, but the range of costs is fairly well understood. Unscheduled maintenance costs are not as readily defined. Experiential data of unplanned events from a large sampling of plants over time can be used to estimate unscheduled costs. Because of the wide variation in experience from unit to unit, a range of costs are anticipated. This paper includes a description of a study of F-class combined-cycle plant data that provides the basis for defining a cost distribution of unscheduled maintenance costs. In addition, the reliability and availability statistics of these plants are used to estimate lost generation revenue due to unplanned outages, which can be significantly higher than the cost of performing the repairs to return the unit to service.