Under what condition does a Balancing Authority's (BA) Area Control Error (ACE) remain at zero?

The Area Control Error (ACE) of a Balancing Authority (BA) is a critical measure used to ensure that the generation of electricity matches the consumption within its control area, taking into account both the scheduled interchanges with neighboring areas and the actual interchange. The ACE is calculated based on the difference between the actual and scheduled interchange and the frequency bias as it relates to the interconnected power system.

When the actual and scheduled interchange are balanced, it means that the net flow of electricity into and out of the Balancing Authority's area matches the forecasted or scheduled amount. In this scenario, there are no discrepancies to correct, resulting in an ACE of zero. This balance is crucial for maintaining system reliability and stability, as it indicates that the Balancing Authority is effectively managing the generation and consumption of power in alignment with scheduled interchanges.

While generation equaling load, stable frequency, and compensated reactive power are all important to the overall operation of power systems, they do not directly correlate to achieving a zero ACE by themselves. Specifically, generation can equal load without necessarily ensuring that actual and scheduled interchanges are perfectly aligned. Consequently, achieving balance in actual and scheduled interchange is the specific condition that results in a zero ACE.