The Electric Reliability Council of Texas (ERCOT) implemented the second stage of its emergency grid procedures following a sudden drop in the system frequency on the evening of Feb. 26.
Preliminary reports indicate the frequency decline was caused by a combination of events, including a drop in wind-energy production at the same time the evening electricity load was increasing, accompanied by multiple power providers falling below their scheduled energy production. In addition, the drop in wind energy led to some system constraints in moving power from the generation in the north zone to load in the west zone, resulting in limitations of balancing energy availability. The wind production dropped from more than 1700 MW three hours before the event down to 300 MW at the point the emergency procedures were activated.
ERCOT skipped the first step of its emergency procedure, which entails instructing all available generation to come on-line and securing emergency power from neighboring electrical grids through dc ties. By moving directly to the second stage, system operators were able to activate ERCOT's demand-response program Loads Acting as Resource, which added approximately 1100 MW within a 10-minute period. Most of the interruptible loads were restored after approximately an hour and a half. No other customers in the ERCOT region lost power due to the event. The emergency procedures were declared at 6:41 p.m. and ended at 9:40 p.m.