Stable Operating Regions of Torsional Interaction Phenomenon in Synchronous Generators

This paper shows that the unstable torsional interaction phenomenon, which had been the cause of shaft failures, is restricted only to the condition when the network resonance frequency and the interacting torsional resonance frequency are both subsynhronous. The interactions, in which this condition is not fulfilled, are positively damped and therefore, safe. The paper also presents physical and analytical insights into the characteristics of the damping torque-vs-frequency curve of the synchronous generator.