What measures the ACE/Frequency ratio?

The ACE (Area Control Error) to Frequency ratio is a critical metric used in transmission operations to assess the accuracy of frequency control within an interconnected grid. This ratio is primarily measured by the Control Performance Standards (CPS), which are designed to ensure that the performance of the control areas in maintaining the balance between generation and load—and hence, system frequency—is within acceptable limits.

CPS evaluates how well a control area can maintain its frequency in the face of disturbances. It incorporates not only the ACE value but also considers the system's frequency response, making it directly relevant to the ACE/Frequency ratio. Maintaining an effective ACE/Frequency ratio is vital for the stability of the power grid because it reflects the area’s ability to manage frequency deviations in relation to its control errors.

The available transfer capability (ATC) relates to the amount of electricity that can be transferred over the grid without violating reliability criteria. Disturbance Control Standards (DCS) focus on the ability to recover from disturbances rather than specifically measuring the ACE/Frequency ratio. Frequency Bias (B) does provide an indication of how much generation or load should be adjusted for changes in frequency but is not the metric that directly computes the ACE/Frequency ratio.

Thus, Control Performance Standards (C