Limiting the Maintenance Impact of Frequency Regulation Duty on Simple and Combined Cycle Gas Turbine Power Plants

Abstract

As more new power plants based on gas turbines enter service, the need for these plants to participate in grid frequency regulation, as opposed to providing blocks of base load power on a dispatchable basis, increases dramatically, exposing this equipment to the potential for accelerated thermal fatigue duty. This paper proposes a methodology for quantifying and limiting the maintenance impact of rapid load changes imposed on gas turbines when required to provide frequency regulation service to the connected utility. The paper includes a discussion of the need for prime movers to participate in system frequency regulation and the impact of this type of service on gas turbine operation. The physics of thermally induced low cycle fatigue is then discussed, and the relationships are quantified using a multiple time constant approach that provides guidance for estimating the transient thermal characteristics of the turbine airfoils that are susceptible to thermally induced low cycle fatigue. This is used to develop the thermo-mechanical relationships that are pertinent to gas turbines in generator drive service. Finally, this material is related back to operational considerations in utilizing gas turbines for system frequency regulation duty.