Drop in NEM Mainland Frequency appearing to coincide with trips at New England Solar Farm, on Saturday 19th April 2025

A couple SMS alerts triggered by ez2view alerted me at 14:39 (NEM Time) on Saturday 19th April 2025 to coincident trips of both units at New England Solar Farm communicated by AEMO via MN126958 as follows:

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MARKET NOTICE
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From :              AEMO
To   :              NEMITWEB1
Creation Date :     19/04/2025     14:39:05

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Notice ID               :         126598
Notice Type ID          :         POWER SYSTEM EVENTS
Notice Type Description :         Emergency events/conditions
Issue Date              :         19/04/2025
External Reference      :         Non-credible contingency event – NSW region – 19/04/2025

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Reason :

AEMO ELECTRICITY MARKET NOTICE.

Non-credible contingency event – NSW region – 19/04/2025

At 1351 hrs the Uralla – New England Solar Farm No.1 330/33 kV Transformer and New England No.2 Solar Farm tripped.

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 event is not known at this stage.

Manager NEM Real Time Operations

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END OF REPORT
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A little later in the afternoon, in checking our 2-hour trend from the live frequency reading from the Mainland NEM (measured in Brisbane at 0.1second cadence) shows a drop that appears to* coincide with the disruption:

* note that the default chart is pretty coarse in terms of what it shows, looking backwards.  Perhaps later we’ll extract the raw data and trend, to see precise times and stats.

We can see the coincident trips of both NEWENSF1 and NEWENSF2 in the 5 minute period ending 13:55 (NEM Time) in the two copies of the ‘Unit Dashboard’ widget in ez2view here:

We can see that the total loss of supply was 349MW … about the size of a coal unit trip.

There was an earlier ‘drop to 0MW’ at NEWENSF1 at 09:40 that has not been investigated.

PS1 more, in Market Notices on Sunday morning

It does not often happen that there’s two Market Notices in quick succession – especially with what seems to be a retraction in the second notice.

First, at 06:23 (NEM Time) was MN126600 as follows:

‘——————————————————————-
MARKET NOTICE
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From : AEMO
To : NEMITWEB1
Creation Date : 20/04/2025 06:23:59

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Notice ID : 126600
Notice Type ID : POWER SYSTEM EVENTS
Notice Type Description : Emergency events/conditions
Issue Date : 20/04/2025
External Reference : Update – Non-credible contingency event – NSW region – 19/04/2025

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Reason :

AEMO ELECTRICITY MARKET NOTICE.

Update – Non-credible contingency event – NSW region – 19/04/2025

Refer AEMO Electricity Market Notice 126598

At 0617 hrs the Uralla – New England Solar Farm No.1 330/33 kV Transformer and New England No.2 Solar Farm 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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Then, at 08:04 (~100 minutes later) was MN126601 as follows:

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MARKET NOTICE
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From : AEMO
To : NEMITWEB1
Creation Date : 20/04/2025 08:04:30

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Notice ID : 126601
Notice Type ID : RECLASSIFY CONTINGENCY
Notice Type Description : Reclassify contingency events
Issue Date : 20/04/2025
External Reference : Update – Non-credible contingency event – NSW region – 19/04/2025

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Reason :

AEMO ELECTRICITY MARKET NOTICE.

Update – Non-credible contingency event – NSW region – 19/04/2025

Refer AEMO Electricity Market Notice 126600, 126598

Further information from the participant revealed the cause of this non credible contingency event is not known at this stage.
AEMO is not satisfied that this non credible event is unlikely to re-occur.
AEMO has therefore reclassified this event as a credible contingency event until further notice.

Region: NSW

Elements: Uralla – New England Solar Farm No.1 330/33 kV Transformer and New England No.2 Solar Farm
Duration: 0745 hrs 19/04/2025 until further notice
Constraint set(s) invoked: Nil

Manager NEM Real Time Operations

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END OF REPORT
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