Updated list of events on 25th May 2021 that we’ll be investigating – time permitting


On Wednesday 26th May (day after the event) in this article we identified that there were 3 events that occurred on the day.

Two days later (on Friday 28th), using the trace of high-speed frequency we’ve been measuring for a while now, we identified that there were were actually four events that happened through the day.

In the following table, I’ve updated the list of events that we are puzzling about, just with respect to events on the day:

Event Label
and Event Time
Description of the Event
Event 0 at 13:33:46.000
(not sure yet)

In this article on Friday 28th May, we identified a (relatively!) small frequency drop down to 49.879Hz.

We’ve not written any more about this – though we have been discussing some theories internally and we also have seen some speculation about this on some social media threads.

Released late on Wed 2nd June 2021, the AEMO’s Preliminary Report notes in the Executive Summary that:

“Initial investigations show that at 1334 hrs on 25 May 2021, Callide C4 ceased exporting active power and was
observed to absorb approximately 50 MW and 300 megavolt-amperes reactive (MVAr) from the power system, …”

That’s not healthy…

Event 1 at 13:44:21.000
(Callide C3 and C4 trip)

This was first noted in the first article in the series.

I named it ‘Event 1’ the next day (Wed 26th May), and then wrote about it on Fri 28th May using ez2view snapshots.

The low point here was 49.773Hz.

Mark Ludlow’s article in the AFR on Wednesday afternoon, 2nd June 2021 provides some excellent additional information I’d not seen before.

Just prior to 17:00 on Wednesday 2nd June, the AEMO’s Preliminary Report was released, provides more details of what went on here.

Event 2 at 14:06:45.803
(Many other units)

We identified this on 26th May, and then wrote about it on 28th May using ez2view snapshots.

The low point here was way down at 48.555Hz.

At this point QNI separated for ~20 seconds (as the Hornsdale frequency data confirmed) and Allan reminds us that some things went right.

Just prior to 17:00 on Wednesday 2nd June, the AEMO’s Preliminary Report was released, and provides some details of Event 2.

Event 3 through to 14:30
(System Strength constraining off Solar Farms and Wind Farms in northern QLD)

We identified this on 26th May using ez2view snapshots, but have not yet had time to follow this one up.

There are a few questions there I’ll be delving into.

Later on Wednesday afternoon (2nd June) I published this ‘Initial look at System Strength constraints’, but will have to wait for more time to do more….

Released late on Wed 2nd June 2021, the AEMO’s Preliminary Report includes a table on this constraint in section 5 (bottom of page 16).

Event 4 – Afternoon and Evening
(Recovery through a very volatile evening)

In the lead-up to the evening we’d issued this warning, and then wrapped up later that night (with a sense of relief) when things had subsided.

Allan’s article showed some of the recovery – and, on Monday this week, I posted this first pass review of bidding on the day.

Carl Daley’s article on Monday 31st May also provided some details.

However there are other questions about this event that we have not explored.

Released late on Wed 2nd June 2021, the AEMO’s Preliminary Report notes in the Executive Summary that:

“The large reduction of generation availability led to actual Lack of Reserve 1 (LOR1) and LOR2 conditions, and
forecast LOR3 conditions in Queensland. Actual LOR1 and forecast LOR2 conditions also occurred in New
South Wales.

As a result of the event, 15 MW of Reliability and Emergency Reserve Trader (RERT) capacity was activated in
Queensland.

Forecast LOR3 conditions in Queensland were subsequently cancelled at 1923 hrs. Investigation is underway
into the reasons for changes in forecast reserve conditions and will be discussed in a later report.

The report also contains a discussion of this in section 6 (starts at the bottom of page 17).

 

There are other questions we’ve asked that are longer-range.

 

When we have a chance to review the AEMO Interim Report (due today) we’ll note it on WattClarity – and then we might flag other events to delve into, in addition to the above….

About the Author

Paul McArdle
One of three founders of Global-Roam back in 2000, Paul has been CEO of the company since that time. As an author on WattClarity, Paul's focus has been to help make the electricity market more understandable.

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