Self Excited Torsional Frequency Oscillations with Series Capacitors

The application of series capacitors to compensate long-distance high-voltage transmission lines introduces potential modes of dynamic instability caused by interactions with synchronous machines and turbine-generator shaft torsional resonance. This paper describes the modes of ihstability and analytical methods used to predict the combinations of parameters which may lead to instability. Insight into the phenomena of modal interaction, a factor causing one of the unstable modes, is provided.