On the 25th of May, an explosion and fire at Callide Power Station initiated a series of events that culminated in blackouts affecting hundreds of thousands of Queenslanders.
The figure below shows the coal power station units at Callide, Stanwell, and Gladstone tripping as this event unfolded between 1:45-2:10pm.
However, when I examined the two Gladstone units that did not trip, I saw something rather interesting. As you can see in the figures below, in response to a sharp drop in system frequency, both units momentarily boosted their output.
This automated response is a textbook example of primary frequency response (PFR) in action. It’s lucky that the roll-out of mandatory PFR had almost been completed at the time, otherwise things could have been far worse!