What effect does a negative ACE have on a Balancing Authority's (BA) CPS1 score when frequency is above schedule?

A negative Area Control Error (ACE) indicates that a Balancing Authority’s actual frequency is higher than the scheduled frequency, which generally means that the Balancing Authority is supplying more generation than currently needed to balance the system. In this context, the Balancing Authority's performance is being evaluated against certain reliability standards, specifically the Control Performance Standard 1 (CPS1).

When frequency is above schedule, having a negative ACE contributes favorably to the CPS1 score because it reflects effective management of the system's generation relative to the load. A negative ACE suggests that the Balancing Authority is maintaining a balance over the specified time interval, which is essential for reliability. By producing more generation than is needed (hence causing the positive frequency deviation), the Balancing Authority demonstrates a capability of effectively managing supply, which positively impacts its CPS1 score.

In summary, a negative ACE under these circumstances indicates that the Balancing Authority is in a favorable position concerning its control over the grid, leading to an improved CPS1 score. The system’s overall reliability is enhanced when a Balancing Authority is proactive and effectively managing its generation resources in response to load changes.