Understanding Grid Disturbances

Example 1: Large Generator Trip

Scenario: A large generator (e.g., a 500 MW power plant) suddenly trips offline.

Effects on System Frequency:

- Immediate Impact: The sudden loss of 500 MW of generation causes an imbalance between supply and demand, leading to a drop in system frequency.

- Frequency Response: Primary frequency control mechanisms, such as governor action, will quickly respond to arrest the frequency decline. Generators with active governors will increase their output to counter the frequency drop.

- Secondary Control: Automatic Generation Control (AGC) will activate to bring the frequency back to its nominal value by adjusting the output of other generators over a longer period.

Impact on ACE:

- Initial ACE Spike: The loss of generation will cause a significant increase in the ACE, indicating a large imbalance.

- Correction: AGC will work to reduce the ACE by adjusting the outputs of other available generators.

Example 2: Large Loss of Load

Scenario: A sudden disconnection of a large industrial load (e.g., a 300 MW manufacturing plant) occurs.

Effects on System Frequency:

- Immediate Impact: The sudden loss of 300 MW of load causes an excess of generation, leading to an increase in system frequency.

- Frequency Response: Primary frequency control mechanisms will respond by reducing the output of generators to arrest the frequency rise.

- Secondary Control: AGC will adjust generator outputs to restore the frequency to its nominal value.

Impact on ACE:

- Initial ACE Spike: The loss of load will cause a significant decrease in the ACE, indicating an excess of generation.

- Correction: AGC will work to increase the ACE back to acceptable levels by reducing the outputs of other generators.

Example 3: Transmission Line Fault

Scenario: A critical transmission line trips due to a fault, isolating a portion of the grid.

Effects on System Frequency:

- Localized Impact: The isolated area may experience frequency deviations depending on the generation and load balance within the islanded portion.

- System-Wide Impact: The remaining interconnected grid may experience frequency deviations if the line carried significant power flows.

Impact on ACE:

- Initial ACE Impact: ACE will reflect changes based on the new balance of generation and load in the control area.

- Correction: AGC will adjust to bring ACE within acceptable limits by redistributing generation.

Visit www.gridopsacademy.com to learn more about system dynamics and disturbances!