NEM demand tragic and occasional WattClarity guest author Allan O'Neil drills into an apparent discrepancy in AEMO's demand calculations following the 1 July 2026 transition of the Basslink interconnector from MNSP market participant to Regulated status.
Guest author (Dr Julian de Hoog) provides some analysis of what has unfolded over the first year of operation of the new Frequency Performance Payments, (FPP) regime - with a particular focus on solar farms.
On or before 13th November 2025, the AEMO published its ‘Frequency Monitoring – Quarter 3 2025’ report:
This afternoon we saw mainland frequency briefly step above its normal operating band for approximately 20 minutes — potentially the result of a data glitch. In this quick piece, we unpack some market dynamics while it unfolded.
Back in July 2025 we saw the AEMO had released this ‘Technical Review of the NEM Frequency Control Landscape’ … but are only noting this here now.
We follow on from A 292MW drop in "Market Demand" in Tasmania, on Saturday 16th August 2025 enlisting this "Part 2" to understand the sequence of events using 4-second data.
Among other aspects, a large dip in solar UIGF aligns with the frequency deviation observed on 19th August 2025.
On Tuesday the 19th of August between 11:45 and 12:20 there was a significant frequency deviation on the mainland.
Various authors have shared articles about frequency, frequency control and Regulation FCAS in recent times (including 6 from Linton). Here's three things that jumped out to me in these pieces of analysis.
The implementation of the Primary frequency response incentive arrangements rule is driving change in how system frequency is controlled and paid-for. The changes stem from how the NEM will incentivise primary frequency response. 6 Years in the making The rule change proposal was initiated July...
The NEM operates at a frequency of 50 hertz (Hz) which means the alternating current should cycle 50 times a second between positive and negative voltage.
Friday 31st January 2025 (appeared to) experienced a very large drop in demand in NSW in a single dispatch interval - but we're now suspecting some form of data/operational glitch. However we wonder, if there was ~1,000MW more energy injected into the grid than required...
It was captured by a keen eyed reader, that the distribution of mainland grid frequency in recent times now exhibits cat ears.
Fourth article on Wed 3rd April 2024, pertaining to the earlier coincident trip of ER01 and ER02 units at Eraring Power Station.
Seven days ago, AEMO notified the market of a Scheduling Error from 24th Jan 2024 to 7th March 2024. A client asked us what it meant - so guest author Allan O'Neil has helped to explore and explain.
Following recent online discussions, Bruce Miller has produced this in-depth analysis of frequency behavior in th NEM.
Allan O'Neil provides an explainer about how small deviations in supply and demand are managed in the NEM, in order to help us understand the apparent swings in frequency that we noted in QLD last Friday.
Another article today presenting 12 hours of history of System Frequency (to ~14:00 on Friday 3rd February 2023) with a few questions added. Comments welcome!
Last week the AEMO released a preliminary report into the trip of the South East – Tailem Bend 275 kV line that caused SA to be islanded from the rest of the NEM for over a week.
Dan Lee takes a quick look at 5-second frequency data to show SA's separation from the rest of the NEM and the ensuing frequency swings on late Saturday afternoon.