Mainland Frequency Wednesday 5th August 2026, how low and when
The nadir we measured was shortly after 16:25: 49.825 Hz, at 16:25:33.
Normal Operating Frequency Band (NOFB)
A quick look at some of the market dynamics around the NEM during this afternoon’s frequency episode
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.
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.
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.
About System Frequency
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.
NEM Mainland frequency patterns – historical overview from 2024
In this overview, we take a longitudinal look back at how frequency has changed over the years.
Drop in System Frequency on Saturday 5th October 2024 – Part 2
To further understand the frequency drop we delve into the 4-second data (used for regulation FCAS contribution calculations) in this Part 2, looking at generating units (including BDUs).
Grid frequency on 13th February 2024
Grid frequency had dropped to 49.689 Hz. We take an initial look into the timeseries of grid frequency recorded on the day.
Investigating last Friday’s frequent frequency swings
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.
What’s “Primary Frequency Response” and why does it matter anyway?
Paul McArdle recently drew my attention to a short Twitter thread started by David Osmond on the arcane topic of NEM system frequency behaviour: At Paul’s invitation I’ve dived further into this issue to fill in some background, provide additional data, and comment on...
Fast Frequency Service – Treating the symptom not the cause?
The National Electricity Market (NEM) is designed to operate at 50 Hz. Frequency deviation occurs when generation and load are mismatched. It is important in a lightly meshed and long network such as the NEM to maintain tight frequency control and that frequency response is...
Let’s talk about FCAS
Ancillary Services Matter! No longer just realm of electrical engineer or energy trading boffins, ancillary services (and particularly Frequency Control Ancillary Services or FCAS which will concentrate on today) have become front and centre in so many ways that barely a day goes by without...