When the Interconnection frequency is at 59.80 Hz and your ACE is a large negative value, what is the recommended action?

When the Interconnection frequency is at 59.80 Hz and the Area Control Error (ACE) is a large negative value, suspending automatic generation control (AGC) and investigating the situation is the recommended action. This scenario indicates a potential imbalance between generation and load that needs to be assessed before taking further action.

A large negative ACE suggests that the area is experiencing a significant deficit in generation compared to the load, which is likely contributing to a frequency that is below the nominal value of 60 Hz. In this instance, the frequency is already low, so simply increasing generation immediately could lead to an even greater frequency drop, posing risks to system stability.

Investigating the cause of the negative ACE allows operators to gather necessary information about load conditions, generation availability, and potential system disturbances. This thorough assessment is crucial because it enables informed decision-making on how to restore balance in the system.

Taking immediate action without understanding the underlying issues could further destabilize the grid. Therefore, suspending AGC is a prudent step to evaluate the condition of the grid, ensuring that any corrective actions taken subsequently are based on a comprehensive understanding of the situation.