The team noted this yesterday (Friday 22nd May 2026) morning … so here’s a quick note to record the sustained period of mild frequency sag (i.e. well within the NOFB, but consistently below the Primary Frequency Response Control Band):
From the following quick look at ‘Dispatch Error’ by Fuel Type, it appears that a sustained period of underperformance of Large Solar assets through the day (including through the period above) would have contributed:
Note the battery and coal units sequentially driving harder the other way through this period, to try to pull frequency back within the PFR Control Band.
Paul was one of the founders of Global-Roam in February 2000. He is currently the CEO of the company and the principal author of WattClarity. Writing for WattClarity has become a natural extension of his work in understanding the electricity market, enabling him to lead the team in developing better software for clients.
Before co-founding the company, Paul worked as a Mechanical Engineer for the Queensland Electricity Commission in the early 1990s. He also gained international experience in Japan, the United States, Canada, the UK, and Argentina as part of his ES Cornwall Memorial Scholarship.
We’ve already looked at how there was a drop in system frequency at ~10:41 NEM time (outside of the NOFB) in conjunction with trips of units at Yallourn Power Station. Well, believe it or not there was a couple drops – not as big – later in the day.
On Wednesday 3rd December, the AEMO held its annual Intermittent Generation Forum and discussed a number of different aspects of challenges and opportunities, including with respect to the frequency weakness on Friday 31st October 2025 contributed to by large aggregate Dispatch Error across Solar Farms
Prior to the Brisbane session of the Nelson Review Panel (on Thu 29th May 2025) we take a look at Dispatch Error in the 16:15 dispatch interval on Monday 26th May 2025 to see who supported frequency, and who drove it the wrong direction (outside of the NOFB).
Whilst there were many things that went wrong on Tuesday 25th May 2021 (last week), guest author Allan O’Neil highlights that there were at least 4 things that went right – contributing to a much less severe outcome than would otherwise have been the case.
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