What mode should an asynchronously operating Balancing Authority switch its AGC to?

• A. Tie line bias control
• B. Flat frequency control
• C. Flat tie-line control
• D. Manual control

Answer: (B)

The correct mode for an asynchronously operating Balancing Authority to switch its Automatic Generation Control (AGC) to is flat frequency control. This mode is particularly suitable for systems that are not interconnected synchronously.

When the Balancing Authority operates asynchronously, it does not have direct control over how the tie lines behave with respect to neighboring systems. Therefore, maintaining a stable frequency across its own generation resources becomes the primary goal. Flat frequency control focuses on keeping the frequency within predetermined limits by adjusting generation resources based on frequency deviations, rather than adjusting for tie-line flows. This method is essential for ensuring system reliability when traditional methods of managing tie lines may not apply.

In contrast, tie line bias control and flat tie-line control are designed for synchronous operations where tie lines can be effectively monitored and controlled based on the interconnections with neighboring Balancing Authorities. Manual control may be necessary in specific situations but is generally less effective than AGC modes for ongoing and automated frequency management.