AEMO declares Scheduling Error – related to the ‘Self-forecast vendor issue’ experienced on 19th August 2025

Back on Tuesday 19th August 2025 there was a large frequency spike that stemmed from a glitch in the self-forecasts submitted by one particular vendor:

1)  across many Semi-Scheduled units

2)  that (for all of these units) presented the UIGF as 0MW

3)  whereas (because no Semi-Dispatch Cap) the units freely produced non-zero output

4)  which totalled a sizeable amount of ‘phantom’ production that was not accounted for in NEMDE

5)  which drove the frequency high, outside the bounds of the NOFB for a considerable period of time.

A couple weeks ago we added to articles already collated by noting that the ‘AEMO frequency monitoring report provides some details of frequency event (due to self-forecast glitch) on 19th August 2025’.

Last week (on Thursday 27th November, whilst I was away) the AEMO made a Scheduling Error Declaration as shown here:

… with that report opening to Incident Number #73 which says:

‘From 1145 to 1215 hrs on 19/08/2025, Uninterrupted Intermittent Generation Forecast (UIGF) for 34 semi-scheduled plant were incorrectly set to zero due to a self-forecast provider software update. This resulted in a generation surplus of approximately 1,550 MW causing the mainland frequency to exceed the Normal Operating Frequency Band (NOFB) upper limit of 50.15 Hz.’

as follows:

A quick note that compensation might be available to affected parties (for instance which might be any unit that provided lower PFR as they have foregone generation at prices that were quite attractive).