Method for Evaluation of the Impact of CAG Operating Mode in the Lifetime of a Francis Hydro Generating Unit Components

摘要

This study presents the methodology developed to evaluate the impact of the Frequency Control Operating Mode (Automatic Generation Control – CAG in a local designation) in the lifetime of hydro generator components. The main characteristic of the operation in frequency control mode is the continuous active power variation to which a Generating Power Unit is submitted in order to keep the National Electrical System’s rated frequency and stability. These active power oscillations lead to an additional dynamic loading on its components and hydraulic structures. In this study two approaches were used: fatigue-based and wear-based, depending on the component under analysis. The fatigue analysis consists in comparing the partial damage for the operation in constant output and frequency control mode in order to quantify the CAG influence in each component fatigue life. Evaluation of the wear was performed for the distributor bushings and considers the amount of relative motion to which they are exposed when the turbine is operating in frequency control mode and an estimated amount outside frequency control mode.