We’ve already noted the ‘Major spike in mainland frequency, on Thursday 6th November 2025’.
What first alerted us to something going awry were a series of ‘Notification’ widget alerts in ez2view, suggesting sequentially large changes in ‘Market Demand’ in Victoria … but we’ll start with this snapshot from NEMwatch at 13:20 (NEM time) on Thursday 6th November 2025 to summarise:
To be clear, what this shows is that the ‘Market Demand’ in Victoria (apparently!) ramped by 1,812MW over 20 minutes:
- From 2,734MW at 12:25
- To 4,546MW at 12:45
… before then dropping by 1,758MW (back to 2,788MW) at 12:50.
Here’s a view of the alerts from ez2view:
Given that there was a large ramp in frequency around the same time, my guess is that:
- There was a data glitch somewhere that caused NEMDE to think that the Grid Demand was increasing steeply (whereas it actually was not);
- Which led to more Scheduled and Semi-Scheduled units receiving higher Targets (which were not necessary);
- Which overcooked the system frequency;
- Until (realisation happened and) corrective action was taken:
- With the phantom increase in demand being removed;
- And Targets returning to normal
- And frequency dropping back to normal.
No Market Notices yet from AEMO, so we’ll see what further details arrive….
If the frequency signal was measuring fine, the error could have been in the AGC delivered set point telling generators to increase output, or in the controller’s understanding of actual supply.
Another error source may have been the automated wind and solar forecasting system? Could that have predicted less wind and solar about to occur?
If the frequency measurement was ok, could the error have gotten into the demand forecasting which in control systems is a feed-forward input to the controller?
Fun times.