How collective under-performance of Semi-Scheduled Solar Farms weakened frequency on Sunday afternoon 30th November 2025

We’ve already posted about how ‘Mainland Frequency dragged downwards around sunset, on Sunday 30th November 2025’,

1)  noting 4 discrete periods of frequency weakness (~17:20, ~17:35, ~17:50 and ~18:10 NEM time on Sunday 30th November 2025):

2)  and (in the process) speculating that this might have been contributed to by some collective under-performance of Semi-Scheduled units over this period.

I’ve taken a few minutes today to use the ‘Trends Engine’ within ez2view to produce this trend of Aggregate Dispatch Error (NEM-wide) for each of the main fuel types in the NEM as follows:

On this chart (showing all 288 dispatch intervals on the day):

1)  I’ve highlighted the same 4 dispatch intervals (noted above with frequency weakness);

2)  And frequent readers here won’t be surprised to learn that, as expected, these periods correlate with:

(a)  collective under-performance of Semi-Scheduled units on each occasion

…. in these 4 cases mainly underperformance of Solar Farms.

(b)  with the main measures for corrective response coming from Battery Units and Coal Units

… again, no surprises there.

3)  Note also some other large deviations across the Large Solar Farms highlighted.

Clearly the current approach is not going to be sustainable, or scalable!  But what to do…