Transient response and life assessment: Case studies on the load rejection of two hydroelectric turbines

Transient events often account for most of the fatigue damage sustained by hydroelectric turbines during operation. Since one of these damageable events is load rejection, this paper presents a study of the dynamic response of two hydroelectric turbines during load rejection. The two turbines are similar in design and in overall measured behavior. However, we observed that the two turbine runners exhibit different deformation patterns. As the observed behavior was not expected at the time of the measurement, the result was that some of the available data was under-sampled. To circumvent this, we developed a method to correct the aliased signal in order to obtain suitable rainflow cycle counts and amplitudes for fatigue analysis. The paper presents the methodology used and an overview of the results obtained for both case studies.