AEMO preliminary report identifies 4 separate Events … including trips* at 4 Generators and 1 Load

As noted on Friday, the AEMO was fast out of the blocks in releasing its Preliminary Operating Incident Report related to ‘Event 2’ that occurred on Tuesday 13th February 2024 in Victoria.

This weekend I’ve been doing some analysis of my own:

1)  starting with this top-down initial review of participant bidding behaviours; and

2)  leading into [TO BE ADDED]

… but I did take time to read through the AEMO report, and thought it worth highlighting that the AEMO:

1)  identifies four discrete Events on the day (so one more than the three events noted in our ‘sequence of events for what happened in Victoria through the day on Tuesday 13th February 2024 (via Timescale #1)’), and

2)  amongst these Events, the AEMO identifies loss of 4 different power stations (whereas to date we’ve only written about three) and 1 major load (which we have not yet written about) … plus the two discrete network sites.

I thought it would be worth listing these all below.

Event 1 – loss of Stockyard Hill Wind Farm

In our earlier ‘sequence of events’ we called this Event 1, so for consistency have kept the same numbering here.

Within Section 2.3 of the report (p8/19), the AEMO writes:

‘Prior to the event, AEMO was managing a sustained low frequency event including the loss of approximately 500 MW of generation from Stockyard Hill WF that occurred at approximately 1135 hrs and had increased the minimum frequency control ancillary service (FCAS) regulation raise requirement. Constraint set F-MAIN_RREG_0450 was invoked between 1200 hrs and 1355 hrs on 13 February 2024 to ensure mainland regulation raise requirement was greater than 450 MW.’

Note (re * in the title of the article) that the AEMO refers to this as a ‘loss’ of generation from Stockyard Hill and not necessarily a ‘trip’.

Readers might remember we showed some of the increased enablement for Raise Regulation FCAS in Friday’s article ‘Aggregate enablement of RaiseReg FCAS from units in the mainland (excluding Basslink) on Tuesday 13th February 2024’.

Event 2 – towers down … the major event

This event is the focus of this Preliminary Report.

Section 1 of the report (p6/19), begins as follows:

‘This preliminary report relates to a reviewable operating incident1 that occurred on 13 February 2024 in Victoria. At 1308 hrs on 13 February 2024, the Moorabool (MLTS) – Sydenham (SYTS) No. 1 and 2 500 kilovolt (kV) lines tripped following failure of six 500 kV towers (three on each of the two 500 kV circuits). The simultaneous trip of these 500 kV lines and subsequent disconnection of all four Loy Yang A generating units, Dundonnell Wind Farm (WF) and Yaloak South WF had a significant impact on the Victorian power system. Initial review indicates Dundonnell WF tripped as designed due to operation of the South West 500 kV special control scheme. In total, approximately 2,690 megawatts (MW) of generation was lost, and 1,000 MW of load was shaken off2 in Victoria following the disturbance.

Following the event, at 1420 hrs on 13 February 2024, AusNet was instructed to shed 300 MW of load to manage loading of in-service network elements. AEMO subsequently instructed load to be restored at 1450 hrs and 1510 hrs.’

I’ve copied this in to highlight two things:

1)  The three stations highlighted as tripping are Loy Yang A and Dundonnell (both of which we have noted before), but also Yaloak South (which we have not noted before);

2)  What also stood out to me was the statement:

‘Initial review indicates Dundonnell WF tripped as designed ….’

… whereas I note that there’s no similar statement there for either Loy Yang A or Yaloak South Wind Farm.  Perhaps I’m reading too much into the absence of similar words – perhaps investigations are more complex for both of those sites?

Event 3 – Hazelwood

This event is not the focus of this Preliminary Report.

In Section 1 of the report (p6/19), the AEMO writes:

‘Later, at 1543 hrs on 13 February 2024, a further separate incident occurred involving trip of the Hazelwood Terminal Station (HWTS) – Jeeralang Terminal Station (JLTS) 220 kV No. 2 line and the offloading of the HWTS 500/220 kV No. 1, No. 2, No. 3 and No. 4 transformers. This incident will be subject to a separate review. ’

4th Event – Trip at Portland Smelter (but perhaps not 4th in chronological sequence)

It’s only mentioned once, on the last page of the preliminary report, where it includes a System Diagram that’s annotated with:

‘Later trip of APD potline’

Here’s it highlighted on the diagram:

… but note that it does not specifically mention a time at which this occurred, other than it happened ‘later’, which I read as ‘later (than Event 2)’ (i.e. Event 4 might 0have actually occurred before Event 3).

PS1 later on Sunday 18th Feb 2024

Later on the same day we ask ‘What happened at Portland Aluminium Smelter?’ with the 4-second SCADA data and see that this event did indeed occur earlier than Event 3.

As noted there, the smelter was offline at ~15:00 and back online by ~15:09.