Jump in mainland System Frequency, coincident with potline trip at Portland smelter

One of the alerts triggered by ez2view overnight was with reference to the content in Market Notice 117908 from the AEMO, published at 01:02:

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MARKET NOTICE
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From :              AEMO
To   :              NEMITWEB1
Creation Date :     28/08/2024     01:02:22

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Notice ID               :         117908
Notice Type ID          :         POWER SYSTEM EVENTS
Notice Type Description :         Emergency events/conditions
Issue Date              :         28/08/2024
External Reference      :         Non-credible contingency event – VIC region – 28/08/2024

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Reason :

AEMO ELECTRICITY MARKET NOTICE.

Non-credible contingency event – VIC region – 28/08/2024

At 0001 hrs the APD No1 Potline and the APD No 2 Potline tripped.

AEMO did not instruct load shedding.

The cause of this non credible contingency event is not known at this stage.

Manager NEM Real Time Operations

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END OF REPORT
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Out of curiosity, this morning I’ve had a look at our trace of mainland frequency to see what happened at the time of the trip:

We can see a jump in frequency that lines up … but still within the bounds of the NOFB.

Referring back to NEMwatch with this snapshot at 08:00 this morning, we can clearly see the drop in ‘Market Demand’ reflected just after* AEMO became aware of the trip.

* remembering that ‘Market Demand’  is a forward looking measure for demand at the end of the dispatch interval used as an input into NEMDE in the dispatch process.

There’s also an earlier jump in demand at ~23:00 NEM time on Tuesday 27th August 2024 that has not been investigated.

Finally, the potlines returned to service, as the AEMO noted in Market Notice 117908:

‘——————————————————————-
MARKET NOTICE
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From :              AEMO
To   :              NEMITWEB1
Creation Date :     28/08/2024     02:17:12

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Notice ID               :         117909
Notice Type ID          :         POWER SYSTEM EVENTS
Notice Type Description :         Emergency events/conditions
Issue Date              :         28/08/2024
External Reference      :         Update – Non-credible contingency event – VIC region – 28/08/2024

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Reason :

AEMO ELECTRICITY MARKET NOTICE.

Update – Non-credible contingency event – VIC region – 28/08/2024

Refer AEMO Electricity Market Notice 117908

At 0134 hrs the APD No 2 Potline was returned to service.

At 0200 hrs the APD No 1 Potline was returned to service.

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.

AEMO will not reclassify this event as a credible contingency event.

Manager NEM Real Time Operations

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END OF REPORT
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Nothing further, at this point.