What was the cause of the coincident trip of Eraring units 1 and 2?

At approximately 13:22 (NEM time) on Wednesday 3rd April 2024 we saw ‘Simultaneous trip of ER01 and ER02 drops mainland frequency in the NEM’.

There were several articles that followed, which were collated here – including Linton’s note that the units returned on Wednesday night 3rd April.  Linton’s article noted AEMO’s MN115497, in which was noted:

‘The cause of this non-credible contingency event has been identified and AEMO is satisfied that another occurrence of this event is unlikely under the current circumstances.’

However I wondered if I could find out, more specifically, what the cause was…


Anything in the bids & rebids?

Curiosity got the better of me this morning so I quickly opened up the ‘Bids & Offers’ widget in ez2view to review bids for both units to see if they provided any clues.

Eraring Unit 1

Here’s the view, filtered for Eraring Unit 1:


I’ve highlighted the rebids pertaining to the trip and the return to service, but they don’t really provide an answer to my question.

Eraring Unit 2

For completeness, here’s filtered for Eraring Unit 2:


But similarly there’s no real answer to my question there.


Elsewhere from Origin?

I could not find anything particular about these outages on the ‘Investors & Media’ section of the Origin website.

… did not think it would be something they would note there, but did check, for completeness.

Nor did I see (or expect to see) anything on social media.


Noted in the AFR

Coincidentally we noted Ben Potter’s article in the AFR ‘Coal power surge raises pressure to extend Eraring’ on Wednesday afternoon.  In that article, Ben wrote”:

‘Origin said the outages at Eraring were caused by faulty software and the units were being brought back online late Wednesday.’

So maybe that’s all we’re going to know, about the cause?


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.

3 Comments on "What was the cause of the coincident trip of Eraring units 1 and 2?"

  1. Ben Potter would be a trusted jourmnalist of the AEMO and other green protagonists. He would therefore be rewarded with exclusives.

  2. Wouldn’t like to unnecessarily speculate but it is quite usual for pairs of adjacent units to share a certain amount of “common” plant and /or interconnections intended to provide reliability and the ability to maintain both units in service whilst minor maintenance activities are undertaken. Given it was simultaneous trip (and the unload seems to be vertical so either an electrical protection operation or turbine trip rather than combustion where the unloading rate would be slower) it looks like it is a secondary system of some sort. Recovery was good. Whenever these Toshiba units- or indeed most large units – trip from high load (normal metal temperatures) they need to cool for a bit before steam can be re-admitted (so called mismatch temperature). So it appears there was nothing really to “fix”. Just sort it out and get the units back on. It does happen, fortunately very rarely, but is the joy of working at the pointy end of a production operation. Something most commentators will never experience let alone understand.

  3. I’d guess it was caused by an incident in the DC distribution system.

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