Methodical Fundamentals for Constructing Startup Assignment Schedules for Combined-Cycle Power Plants Considering Damage Accumulation

Abstract

Depending on the requirements for power plants at thermal power stations (TPS), alternative approaches can be used for constructing assignment schedules to start power units from different initial thermal states. This issue becomes topical for combined-cycle power plants (CCPP) with heat-recovery steam generators (HRSG) whose thermal cycle includes gas turbines featuring excellent maneuverability and a steam system with equipment characterized by a relatively low loading rate. This paper examines an approach to construction of assignment schedules for CCPP starting based on accumulation of damages of the most heavily loaded thickwall elements in the steam path to meet the requirements for CCPP maneuverability during the entire service life of a CCPP. A principle is proposed for constructing an assignment schedule for starting a CCPP from any initial thermal state within the desired time provided that the number of these startups would not exceed the prescribed limit value determined in assessing the damage accumulation. Assignment schedules must be prepared based on the monitored temperature conditions of CCPP equipment, the allowable limits for predicted temperature stresses, and the allowable number of cycles determined by the low-cycle fatigue.