The NEM’s AGC heartbeat failed for some a period of time (unknown currently), ending on Wednesday 12th August 2026

A week ago today was Wednesday 5th August 2026, and the NEM experienced a significant real event (a drop in frequency outside of the NOFB) – for reasons unknown at this point, but which we hypothesise is due to some kind of hallucination in the data feeding into the NEMDE dispatch process:

1)   In other words (and if our hypothesis is correct), a real event triggered by some imagined event.

2)  We’ve currently collated 6 articles in the focused category ‘2026-08-05 Frequency Drop (a significant one due to data glitch)’, and will likely add more as we learn more.

A week later (Wednesday 12th August 2026)  and it’s Ekka Day in Brisbane, so I was not working … but also not at the Ekka either.  Catching up on internal conversations this evening over dinner, I see some non-Brisbane members of our team pointed to MN144798 published at 12:32:03 as follows:

‘——————————————————————-
MARKET NOTICE
——————————————————————-

From : AEMO
To : NEMITWEB1
Creation Date : 12/08/2026 12:32:03

——————————————————————-

Notice ID : 144798
Notice Type ID : GENERAL NOTICE
Notice Type Description : Subjects not covered in specific notices
Issue Date : 12/08/2026
External Reference : HEART BEAT SERVICE RESUMPTION

——————————————————————-

Reason :

AEMO ELECTRICITY MARKET NOTICE

SERVICE RESUMPTION

AEMO advises participants that the service interruption relating to: AGC Heart Beat has been resolved.

Participants experiencing any further service issues should contact the AEMO Support Hub
Phone: 1300236600 Opt1
Email: supporthub@aemo.com.au

Manager NEM Real Time Operations

——————————————————————-
END OF REPORT
——————————————————————-‘

Now, I don’t have time to delve into more detail at this point, but just flagging a few questions we might explore later:

Q1)  When did this failure start?  

… oftentimes when closing off some incident or or system state or intervention/direction etc, the AEMO might refer back to some prior Market Notice that announced the issue.

(a)  There’s none here (and could not find earlier in quick search via the ‘Market Notices’ widget in ez2view)

(b)  So it does leave the question about when the failure started?

Q2)  I am presuming that Regulation FCAS was affected … but what happened to system frequency, more generally?

… and more.