Series Capacitor Controls and Settings as Countermeasures to Subsynchronous Resonance

The investigation of subsynchronous resonance (SSR) [1] by utilities and manufacturers has resulted in proposed and applied methods to mitigate or eliminate SSR damage to turbine- generators. A companion paper [1] presented many of the methods and devices that can be used as countermeasures, solutions or mitigators for the SSR problem, but left to this later paper a discussion of the place of series capacitor controls and settings. The control or adjustment of series capacitors as an SSR countermeasure has also received much attention. This report presents the most common system conditions which lead to large shaft oscillatory torques for turbine- generators connected to series-compensated transmission systems and describes the series-capacitor controls and settings which have been applied or proposed, as countermeasures to limit such torques and torsional interaction [2].