Risk Based Assessment of Unplanned Outage Events and Costs for Combined Cycle Plants

Abstract

Unexpected outages and maintenance costs reduce plant availability and can consume significant resources to restore the unit to service. This paper describes a survey and analysis of unplanned outage events for 388 combinedcycle plants, based on 164 D/EClass and 224 FClass gas turbines. The 15year timeframe included over 3000 unityears of data. The causes and durations of forced outages and unscheduled maintenance were identified, and overall reliability and availability were established for each class of plant. Costs to restore the unit to service for each main outage cause were estimated, as were net revenues lost due to unplanned outages. A statistical approach to estimated costs and lost revenues provides a riskbased means to quantify the impact of unplanned events on plant cash flow as a function of class of gas turbine and plant subsystem. The riskbased assessment defines the range of probable costs of unplanned outage events.