Electric Reliability Council of Texas (ERCOT) Practice Test

Power System Stabilizers are tuned to damp low-frequency electromechanical oscillations that occur in the 0.2 Hz to 2.0 Hz range. They work by sensing a generator’s speed or frequency deviation and injecting a stabilizing signal into the excitation system to increase damping of these oscillatory modes. This band covers both local modes (around the lower end) and inter-area modes (up to about 2 Hz), which are the oscillations PSS is designed to suppress. Frequencies below 0.2 Hz are generally addressed by other control actions, while frequencies above 2 Hz are not effectively damped by PSS and can interact unfavorably with faster AVR actions.