Sharp mainland frequency drop, with trip of CPP_4 on Sunday evening 26th October 2025
The Callide C4 unit tripped from 420MW in the 5 minutes to 18:36 (NEM time) on Sunday evening 26th October 2025, delivering a sharp drop in mainland frequency.
frequency disruption
A collation of articles pertaining to some larger disruptions in system frequency (such as outside of the Normal Operating Frequency Band – NOFB).
Two *big concerns* that we urge the Nelson Review panel to (re)consider (with respect to Invisible Responses) following review of the Draft Report
With All Energy happening this week in Melbourne, plus the clock ticking down on preparations at the Nelson Review Panel for their final report, I've reached back to the NEMdev conference to write about...
Taking a first focused look at the 16:50 dispatch interval on Thursday 16th October 2025 (with frequency dropped below NOFB) … Part 3
In Part 3 of this series with respect to Thursday 16th October 2025, we focus on when a large collective under-performance across all Semi-Scheduled Wind Farms and Solar Farms dragged the frequency outside the...
Peeling the second layer of the onion, with respect to the (SemiSched-induced) frequency weakness on Thursday 16th October 2025
Having already noted the ‘Weakness in frequency stability on Thursday afternoon 16th October 2025’, we take a look at the causes - for the four high-profile dispatch intervals.
Aldoga Solar Farm on Sunday 12th October 2025 – Part 2
In this article we inspect power deviations from dispatched units that would have contributed to the frequency rise, and the deviations that would have contributed to the correction.
Weakness in frequency stability on Thursday afternoon 16th October 2025
The worst periods of frequency stability on Thursday 16th October 2025 were *not* with the simultaneous trip of YWPS3 and YWPS4, but rather later and the day - and look similar to patterns seen...
Simultaneous trips at YWPS3 and YWPS4 on Thursday 16th October 2025
A short note on Thursday 16th October 2025 to record both Yallourn Units 3 &4 tripping during the 13:35 dispatch interval (NEM time) today.
Small spike in Mainland Frequency, with (apparent) ~400MW trip of demand in Queensland on Tuesday morning 14th October 2025
It appears that there was some large(ish) trip in demand somewhere on the Queensland network, given the spike in frequency at ~07:28 on Tuesday 14th October 2025.
Two bouts of >2 hours of Non-Conformance at Aldoga Solar Farm on Sunday 12th October 2025
A quick initial look at two lengthy periods of Non-Conformance at Aldoga Solar Farm on Sunday 12th October, with the first period seeing large negative Dispatch Error, and a blip in system frequency.
NEM Mainland Frequency wanders south as the sun sets, on Thursday 2nd October 2025
A very short article recording another instance of frequency wandering south as the sun is setting (this one on Thursday 2nd October 2025).
A brief recap of a large afternoon frequency wobble on the NEM mainland on Saturday 20th September 2025
We noticed yesterday (Saturday 20th September 2025) a large afternoon dip in frequency down towards (but not outside) the limits of the NOFB - and briefly explore here.
Belatedly highlighting the AEMO’s ‘Technical Review of the NEM Frequency Control Landscape’ from July 2025
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.
Frequency drop on Thursday evening 11th Sept 2025 with Tallawarra B trip
A quick article to explore a frequency drop on Thursday evening 11th September 2025.
Highlighting particular (frequency and/or AggROT) events through 2024 and 2025
In this article, we tie together various events since 1st January 2024 that featured either System Frequency outside the NOFB and large AggROT for Semi-Scheduled assets.
Looking more at (commissioning) operations at Waratah BESS through August 2025
In this article we take a look at operations of Waratah BESS through August 2025 - including some large Dispatch Errors on several days: (a) including Fri 29th Aug 2025, and how WTAH1 apparently...
More about that decay of mainland frequency at lunchtime on Friday 29th August 2025 (i.e. Part 2)
Taking a second look at the midday decay of mainland frequency on Friday 29th August 2025.
Mainland frequency drop with Loy Yang A1 trip on Saturday evening 30th August 2025
On Saturday evening 30th August 2025 there was a trip (and then subsequent recovery) of the Loy Yang A1 unit - we take a look at frequency change.
Decay of mainland frequency at lunchtime on Friday 29th August 2025
As another case of frequency disruption on the mainland grid, we spotted this trend occurring just before midday on Friday 29th August 2025.
Tasmanian demand drop on 16 August 2025 – part 2
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.
Frequency change with Yallourn unit 2 trip
We assess whether the trip at Yallourn 2 on 26 August 2025 was large enough to drive a frequency disturbance.