Some rapid fluctuations in NEM Mainland Frequency – on Tuesday afternoon/evening 29th October 2024

A short article to flag a couple rapid (and noticeable) fluctuations in Mainland Frequency that we spotted this afternoon/evening on Tuesday 29th October 2024.

Event #2 (bottoming at 18:00:29.8)

Here’s one we spotted on the web-based frequency reading:

The chart (and the readings) work in UTC, so in the comments we’ve adjusted for ‘NEM time’.

Note that the rapid dip-and-recovery:

1)  Included a depth of 49.888Hz at 18:00:29.8 according to the measurements on our high-speed frequency device.

2)  Incorporating a drop of 0.062Hz in just under 4 seconds.

We can see this in more detail via this zoomed-in trend (focused just on within the 18:05 dispatch interval) with data extracted from the frequency monitor:

Because this dip-and-recovery took only a few seconds down-and-back, we did not expect to see anything occurring on a dispatch interval timeframe …

Perhaps something might be more visible with the 4-second SCADA data from AEMO, when that’s available?  If time permits, one of the team might have a look

Event #1 (bottoming at 17:31:28.1)

In exploring the data extract, we also spotted another event about a half hour earlier, as shown here:

In this case, there are more gyrations seen on the timestep of fractions of a second:

1)  The low-point was 49.883Hz at 17:31:28.1 according to the measurements on our high-speed frequency device.

2)  There were some gyrations on the way down, which makes it difficult to measure rate of decline – but there was a clear jump of 0.054Hz immediately after the nadir in only 0.1 seconds.

We’ll leave this here as food for thought … one of the team might have more time to number crunch in the coming weeks (no promises!).