When there is a loss of external load, ACE typically does what?

When there is a loss of external load, the Area Control Error (ACE) typically stays the same initially because ACE is a measure of the imbalance between scheduled and actual power. When a power system experiences a loss of load, the instantaneous power generation may still meet the reduced demand without immediate changes in system frequency or generation levels. As a result, the ACE, which takes into account both frequency differences and the interchange between areas, reflects that balance at that moment. Over time, however, as system operators respond to the load changes through adjustments in generation, the ACE may not remain static; it might fluctuate as the system stabilizes. Understanding these dynamics is essential for effective operation and management of power systems within the PJM framework.