System frequency during simultaneous trips at YWPS3 and YWPS4 on Thursday 16th October 2025
System frequency remained within the NOFB, appears well managed given the supply loss approached 600 MW.
system frequency
Four hours of Mainland Grid Frequency, on Sunday 12th October 2025
As something we might refer back to later, here’s a 4-hour trend of NEM Mainland Grid Frequency on Sunday 12th October 2025 – from 09:00 to 13:00 (NEM time).
Also difficult to see any fluctuation in Mainland Frequency on Sunday morning 5th October 2025, with BW02 offline (two-shifting)
Not seeing any obvious blip in system frequency (at the time BW02 came offline on Sat 4th Oct 2025) we also looked at the similar outage on Sun 5th Oct 2025.
Difficult to see any fluctuation in Mainland Frequency on Saturday morning 4th October 2025, with BW02 offline (two-shifting)
I was keen to see if there was any noticeable blip in System Frequency resulting from the BW02 unit coming offline on Saturday 4th October 2025 for the brief (two-shift) outage.
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.
Daily NOFB exceedances since 2021
We count the number of days each month when there was at least one 4-second measurement outside the NOFB.
Instances of system frequency outside the normal operating band
How common is it that mainland frequency deviates outside the NOFB (normal operating frequency band)?
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.
Unit deviations from target on Tuesday 19th August 2025
It appears it was unit availability used to set the target for dispatch that went awry, rather than unit output.
High level view of some contributing factors to 19 August frequency spike
Among other aspects, a large dip in solar UIGF aligns with the frequency deviation observed on 19th August 2025.
Mainland Frequency Spikes to 50.2 on Tue 19th August 2025
On Tuesday the 19th of August between 11:45 and 12:20 there was a significant frequency deviation on the mainland.
Frequency change associated with coal generation events
System frequency shows improved resilience to sudden coal generation events since 2020.
The frequency of coal generation events in 2025
A count of coal generator events indicates large unit trips are less frequent.
Drop in mainland frequency on 16 June 2025
In reviewing system frequency on the 16th of June, 2025, we observed a drop that reached below the NOFB.
Drop in mainland system frequency on 26 May 2025
The measurements indicated frequency ducked just below the NOFB briefly, reaching 49.843 Hz.
Mainland system frequency in the afternoon of April 10, 2025
At 16:01 on April 10, 2025, a system frequency dip was observed from the Global-Roam frequency logger.
Mainland system frequency on April 10, 2025, associated with VIC transmission outage
High speed frequency measurements provide a deeper understanding of how the system responded to the unplanned 500kV line outage.
Three headline observations, about the use of proxies for System Frequency in Frequency Control mechanisms
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.
Comparing Frequency Measures (Frequency, FI, FM)
The faster-moving nature of the FM, with the introduction of FPP, removes predictability in the indicator for frequency performance.