AEMO incident report released, on Frequency Spike due to Self-Forecast Vendor glitch (19th August 2025)
About the AEMO’s Reviewable Operating Incident Report ‘Self-forecasting errors and frequency excursion on 19 August 2025’.
2025-08-19
A collation of articles pertaining to Tuesday 19th August 2025. On this day …
1) We saw a continuation of Administered Pricing for all 10 x FCAS products in the South Australian region:
(a) following the initial triggering of AP on Saturday 17th August 2025.
(b) which flowed from an outage on one Tailem Bend – Tungkillo 275kV line (represented in the ‘S-TBTU’ constraint set)
2) We also saw a large frequency spike across the NEM lasting ~30 minutes and outside of the Normal Operating Frequency Band in the middle of the day.
AEMO declares Scheduling Error – related to the ‘Self-forecast vendor issue’ experienced on 19th August 2025
Last week (on Thursday 27th November) the AEMO made a Scheduling Error Declaration about the sizeable glitch in a particular self-forecast vendor that delivered phantom production on Tuesday 19th August 2025 and a large frequency spike.
AEMO frequency monitoring report provides some details of frequency event (due to self-forecast glitch) on 19th August 2025
Adding to the list of articles we've collated about the frequency disturbance on Tuesday 19th August 2025, we're copying in what AEMO published in its 2025 Q3 monitoring report about the glitch.
On 27th October 2025, AEMO declared Scheduling Error #73 (with respect to 19th August 2025)
A belated and back-dated article, dated for 27th October 2025, which was when the AEMO declared a ‘Scheduling Error’ – Incident #73 with respect to 19th August 2025
Looking more at (commissioning) operations at Waratah BESS through August 2025
In this article we take a look at operations of Waratah BESS through August 2025 - including some large Dispatch Errors on several days: (a) including Fri 29th Aug 2025, and how WTAH1 apparently helped to drive frequency the wrong way; (b) and Tue 19th...
Peeling the onion a little more – Solar Farm performance on Tuesday 19th August 2025, with the frequency spike to 50.2Hz
As the 5th article in an evolving series that progressively explores the (apparent self-forecasting glitch and) frequency spike on Tuesday 19th August 2025, we take an early look at Solar Farm performance.
Administered Pricing for FCAS services in South Australia ended on Sunday 24th August 2025 … so what’s next?
On Sunday 24th August 2025, Administered Pricing for FCAS in South Australia ended ... when will the ‘S-TBTU’ constraint set re-emerge?
Three broader questions (re)triggered by the Frequency Spike on Tuesday 19th August 2025
The (concerning) frequency spike across the NEM in the middle of the day (Tuesday 19th August 2025) has triggered many proximate questions - understandable - but also has raised these 3 Broader Questions.
Unit deviations from target on Tuesday 19th August 2025
It appears it was unit availability used to set the target for dispatch that went awry, rather than unit output.
A ~50-day view of rising spurts of volatility in the LOWER1SEC FCAS market in South Australia
With Administered Pricing in South Australia ongoing today, we take a longer-term look (across the past ~50 days) in the escalating pressure on Cumulative Price for LOWER1SEC FCAS in South Australia.
Network outage on Tailem Bend – Tungkillo 275kV line ended Tue 19th Aug, but Administered Pricing Continues into Wed 20th Aug (part 3)
Part 3 in an evolving series of articles about a series of the network outage(s) on the Tailem Bend - Tungkillo 275kV line that's driven LOWER1SEC prices through the roof and triggered Administered Pricing for FCAS in South Australia
High level view of some contributing factors to 19 August frequency spike
Among other aspects, a large dip in solar UIGF aligns with the frequency deviation observed on 19th August 2025.
Mainland Frequency Spikes to 50.2 on Tue 19th August 2025
On Tuesday the 19th of August between 11:45 and 12:20 there was a significant frequency deviation on the mainland.
Part 2 with respect to Administered Pricing for Lower 1 second FCAS (and 9 other services) in South Australia
With Administered Pricing of all 10 x FCAS products in South Australia continuing into Monday 18th August 2025 (no surprise there), we take a second look.