To be clear, on the timing of the response of this generators, some did some minor adjustments (1MW) as part of regulation FCAS, the moment they dropped below 50Hz.
The interesting thing here is the speed with which Tesla responded to the contingency FCAS market, which is triggered after frequency gets to 49.8Hz. That was pretty much instantaneous. And they did it from a standing start, unlike the other generators.
Tesla weren’t officially playing in that market, but just wanted to show what they could do. And they did. That’s what’s impressive, and what’s game changing.
As for timing, Loy Yang A started to lose it at 1.58:59 (NEM time). Its biggest drop, from 364MW to 176MW, was at 1.59:19, which is where frequency hit 49.8Hz, and which is where Tesla came in a matter of milliseconds (but recorded in the 1.59:23 time frame).
Gladstone 1, a contingency FCAS supplier, hopped in at 1.59:27. Loy Yang was down to 44MW by then and completely gone in the next 4 second period.