AEMO incident report released, on Frequency Spike due to Self-Forecast Vendor glitch (19th August 2025)

Yesterday (Monday 11th May 2026) I was alerted by some keen readers to the release of the AEMO’s Reviewable Operating Incident Report ‘Self-forecasting errors and frequency excursion on 19 August 2025’:

I’ve only just flipped through the report – but see that this should go some way to answering these ‘… questions (re)triggered by the Frequency Spike on Tuesday 19th August 2025’ that I asked back in August, soon after the incident.

One of our team members have found that the following specifically resonated …

A small number of unit responses not consistent with …

from p8/27 in Table 1 – Finding/Risk/Issue #5

‘AEMO’s analysis on PFR and contingency FCAS performance of NEM generators identified a small number of individual units with frequency response not consistent with their PFR or contingency FCAS expectations

However, AEMO has concluded that the majority of units complied with their PFR and contingency FCAS expectations and that the aggregate response to this event was satisfactory.’

… and Recommendation /ongoing action #11

‘AEMO will continue working with generators to implement PFR where it is yet to be implemented.’

… which might segue back to my earlier question ‘Which Semi-Scheduled units are registered to (and) provide PFR?’.

Large deviations might require more FCAS …

Also from p8/27 in Table 1 – Finding/Risk/Issue #6

‘The magnitude of the dispatch error exceeded the size of deviations typically managed through regulation FCAS. Lower regulation FCAS operated satisfactorily, with reserves fully utilised. However, due to the large dispatch error, which was outside the scale of deviations regulation FCAS is intended to manage, frequency could not be maintained within the NOFB.’

… which speaks to the types of questions that we’ve been asking about with respect to ‘Is the Semi-Scheduled Category Sustainable or Scalable?’.

This (single self-forecast vendor failure) speaks to one particular manifestation of this … but there’s an unresolved question about whether the root cause is the Semi-Scheduled category’s looser requirement to watch, and adhere to, a Target.

Hence Recommendation /ongoing action #12 was of interest:

‘AEMO will assess the minimum regulation FCAS quantities required to correct large-scale dispatch errors and determine whether an increase in the minimum regulation FCAS requirement is warranted. AEMO will also explore the option of dynamically  determining regulation FCAS volume, allowing procurement volumes to vary based on requirements.’

We’ve been party to various discussions about dynamically varying Regulation FCAS requirements (such as in relation to MW under SDC, or total volume of UIGF, etc)

Happy reading…