Early this evening we published what ends up to be a ‘Part 1’ Review of some of the incidents that occurred across the NEM on Sunday 24th January 2021 – a hot day in the southern half of the NEM.
Amongst the events, I noted that there was elevated demand and some pricing activity in South Australia. Well, that has continued through the evening and so I thought it might be useful to add a couple notes about what happened later…
(A) Transmission lines trip due to bushfire event
At 18:29 the AEMO issued Market Notice 82348 speaking about the trip of several transmission lines connecting into the Cherry Gardens substation in the Adelaide Hills:
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MARKET NOTICE
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From : AEMO
To : NEMITWEB1
Creation Date : 24/01/2021 18:29:56
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Notice ID : 82348
Notice Type ID : POWER SYSTEM EVENTS
Notice Type Description : Emergency events/conditions
Issue Date : 24/01/2021
External Reference : Non-credible contingency event – SA region – 24/01/2021
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Reason :
AEMO ELECTRICITY MARKET NOTICE.
Non-credible contingency event – SA region – 24/01/2021
At 1646 hrs the following Lines tripped in the SA region
Tailem Bend – Cherry Gardens 275 kV Line
Cherry Gardens – Mount Barker South 275 kV Line
Cherry Gardens – Mt Barker 132 kV Line
AEMO did not instruct load shedding.
AEMO has not been advised of any disconnection of bulk electrical load.
The cause of this non credible contingency has been being identified.
Constraint Set S-CGTB1 invoked from 1655 hrs
Manager NEM Real Time Operations
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END OF REPORT
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The AEMO notice (presumably typed in a rush) is unclear about whether the cause has been identified (or not). However social media provides some strong clues that bushfires were involved …
I noted this tweet at 18:48 (think that is at NEM time) that provided a photo of the bushfires at work around Cherry Gardens in South Australia:
… and here’s an earlier shot from MP (and former SA Energy Minister) Tom Koutsantonis:
… and a note from the Country Fire Service at 19:05:
(A1) Were there any immediate trips?
Using Time-Travel in ez2view to look at the end-of-interval values for the 16:50 dispatch interval we see that there were several things that happened coincident with the loss of the network elements:
1) We see that the TOTAL DEMAND fell by 233MW from 2,685MW (at 16:45) to 2,452MW (at 16:50) … but note that these are forecasts published at the start of the period for what would happen at the end. Dispatch price dropped from $41.37/MWh to $34.20/MWh as a result.
2) In response to one or both of these factors (i.e. the drop in Target Scheduled Demand, and also the network trip) we see changes in generation:
(a) both Port Stanvac (-58MW) and Lonsdale (-15MW) reduced generation down to virtually nothing, and also that there was a 51MW aggregate reduction at Torrens Island units.
(b) there were also a variety of changes (both up and down) at Semi-Scheduled assets, but these were probably just natural ‘follow the sun or wind’ variations – and not as a result of either of the above factors.
(A2) What’s in Constraint Set ‘S-CGTB1’ – invoked from 16:55?
As noted in the Market Notice above, the constraint set ‘S-CGTB1’ was invoked from the next dispatch interval:
As noted here, the Constraint Set is invoked (at this point) to last until 12:00 the following day (i.e. Monday 25th Jan). There are numerous constraint equations as members of this set.
(A3) Bound constraint equation ‘S>>CGTB1_TBTU_TBMO’
As shown above, only one constraint equation ‘S>>CGTB1_TBTU_TBMO’ is bound in the first dispatch interval it is invoked for (16:55):
… so the constraint seeks to:
1) ‘constrain down’ output from Ladbroke Grove, Snuggery, Tailem Bend Solar, Lake Bonney 2 and 3 (noting Lake Bonney 1 and Canunda are Non-Scheduled), and also output from the Lake Bonney BESS
2) ‘constrain down’ flow west over the Heywood AC interconnector … noting that the factor or +1.0 is slightly higher than for any of the other elements.
3) ‘constraint up’ any charging on the Lake Bonney BESS.
All of these actions combine to limit the aggregate LHS to no more than 255.31MW.
(A4) Flow west on Heywood is reduced
The Heywood interconnector becomes bound for the 17:00 dispatch interval:
… however note that the effect in this dispatch interval is moreso a significant reduction in Export Limit (i.e. MAX flow west) than a reduction in Target Flow (only slight at this point).
(A5) Flow west on Heywood is reduced
The Heywood interconnector becomes bound for the 17:00 dispatch interval:
So it starts with a ~60MW reduction in supply to Adelaide from the southern part of South Australia…
(B) AEMO increases the Lack of Reserve Level Alert
At 18:44 the AEMO published Market Notice 82349 that highlighted that the South Australian region had entered an Actual LOR2 Low Reserve Condition from the 18:40 dispatch interval … which would be, at least in part, because of the trip of all of those transmission lines:
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MARKET NOTICE
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From : AEMO
To : NEMITWEB1
Creation Date : 24/01/2021 18:44:54
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Notice ID : 82349
Notice Type ID : NON-CONFORMANCE
Notice Type Description : Details of Non-conformance/Conformance
Issue Date : 24/01/2021
External Reference : Actual Lack Of Reserve Level 2 (LOR2) in the SA region – 24 jan 2021
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Reason :
AEMO ELECTRICITY MARKET NOTICE
Actual Lack Of Reserve Level 2 (LOR2) in the SA region – 24 jan 2021
An Actual LOR2 condition has been declared for the SA region from 1840 hrs.
The Actual LOR2 condition[is forecast to exist until 1900 hrs.
The capacity reserve required is 222 MW
The minimum reserve available is 213 MW
AEMO is seeking an immediate market response.
An insufficient market response may require AEMO to implement a AEMO intervention event.
Manager NEM Real Time Operations
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END OF REPORT
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This snapshot taken from ez2view the SA dispatch price hit $10,578.87/MWh at 18:45 (NEM time) … and was forecast to reach $15,000/MWh in the P5 predispatch forecast for the 18:55 dispatch interval:
At this point, we see only 191MW of Available Generation capacity spare across the South Australia region of any type, and at any price. This has happened in large part because the export flow over Heywood from Victoria has been constrained down further … to only 28MW west in the 18:45 dispatch interval.
I’m not sure why the Lake Bonney BESS is not charging any more – with the price being what it is? Does not seem likely that it’s full, given it had been discharging more than charging over the past couple hours (we see this in the trended capacity factor charts in the ‘SA Schematic’ widget).
(C) Makes it through to the other side…
On this occasion, South Australia made it through to the other side. This LOR2 Low Reserve Condition was cancelled at 19:10 in Market Notice 82351 issued at 19:14:
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MARKET NOTICE
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From : AEMO
To : NEMITWEB1
Creation Date : 24/01/2021 19:14:14
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Notice ID : 82351
Notice Type ID : RESERVE NOTICE
Notice Type Description : LRC/LOR1/LOR2/LOR3
Issue Date : 24/01/2021
External Reference : Cancellation of Actual (LOR2) condition in the SA region – 24 Jan 2021
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Reason :
AEMO ELECTRICITY MARKET NOTICE
Cancellation of Actual (LOR2) condition in the SA region – 24 Jan 2021
The Actual LOR2 Condition in the SA Region advised in AEMO Electricity Market Notice No.82349 is cancelled at 1910 hrs 24/01/2021
Manager NEM Real Time Operations
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END OF REPORT
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Note, however, that this was not the end of it all, as the price did escalate from $1,015.14/MWh (at 19:10) to $4,065.87/MWh (at 19:15) and the IRPM remained low:
As shown in the image above for the 19:15 dispatch interval, NEMwatch calculated that the ‘Instantaneous Reserve Plant Margin’ (i.e. IRPM) for the SA-only ‘Economic Island’ formed by virtue of the constrained imports was down at only 6%.
1) As noted in the image, there was only 161MW of spare generation capacity of any type in that 5-minute period.
2) No surprise that the dispatch price at 19:15 had spiked to $4,065.87/MWh!
The price spike at 19:15 was the last price spike above $1,000/MWh for the day in South Australia … at least at the time this was published!
At 20:13, the AEMO issued Market Notice 82353 cancelling the LOR1 Low Reserve Condition warning.
PS1… Constraint Automation used to manage Power System Security in South Australia
At 21:28 (i.e after this was published, the AEMO issued Market Notice 82355 that noted:
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MARKET NOTICE
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From : AEMO
To : NEMITWEB1
Creation Date : 24/01/2021 21:28:12
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Notice ID : 82355
Notice Type ID : INTER-REGIONAL TRANSFER
Notice Type Description : Inter-Regional Transfer limit variation
Issue Date : 24/01/2021
External Reference : Inter-regional transfer limit variation – SA Region – 24/01/2021
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Reason :
AEMO ELECTRICITY MARKET NOTICE
Inter-regional transfer limit variation – SA Region – 24/01/2021
To manage Power System Security in the SA Region, the following constraint set has been invoked.
Constraint CA_BRIS_4F1FE461_1 invoked from 2120 hrs until further notice
Constraint has the following interconnector on the LHS
VIC1-SA1
Manager NEM Real Time Operations
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END OF REPORT
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No time to dig any further, tonight…
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