More about that decay of mainland frequency at lunchtime on Friday 29th August 2025 (i.e. Part 2)

On Friday 29th August 2025 we’d seen and briefly noted a ‘Decay of mainland frequency at lunchtime on Friday 29th August 2025’.

With a 3-hour time range (10:00 to 13:00 NEM time) of extracted data from one of our Brisbane-based measurements of mainland frequency at 0.1 second cadence, we see the following:

Now, coincidentally with respect to the ‘Mainland frequency drop with Loy Yang A1 trip on Saturday evening 30th August 2025’, it’s useful to compare and contrast:

1)  Clearly the decay and subsequent recovery were more gradual than the rapid drop (and recovery) with the trip of LYA1

2)  But we do also see the drop was deeper

(a)  in this case, the lowest point* was 49.847Hz (just outside NOFB) at 11:50:30.8 on Friday 29th August 2025

(b)  which is outside of the NOFB (slightly)

3)  Additionally, we can see:

(a)  more variability of frequency during ‘strong daylight hours’ (10:00 to 13:00) given the challenges of managing frequency with invisible rooftop PV (amongst other things).

(b)  compared to the ‘sunset hours’ time range selected here.