Market Notices

AEMO ELECTRICITY MARKET NOTICE

AEMO will increase the Heywood test limit from SA to Vic (from the current 550 MW) to 600 MW today to conduct internetwork testing on Heywood.

The following constraint sets will be revoked once the testing criteria met:
I-SV_HEY_550_TEST

The following constraint sets will be invoked:
I-SV_HEY_600_TEST

AEMO will revert the Heywood test limit back to 550 MW once the test has completed while the test result being analysed.

Please also refer to the published formal PEC Stage 1 and HIC capacity release testing information at the following link: https://aemo.com.au/-/media/files/stakeholder_consultation/consultations/nem-consultations/2023/project-energyconnect-stage-1-and-hic-capacity-release/pec-stage-1-and-hic---final-test-program.pdf?la=en.

Terry Liu
AEMO Operations

Refer to Market Notice 134696

AEMO has now completed the production of the Murraylink dynamic rating forecast model and the forecasting performance has been satisfactory during the test. AEMO will be enabling the pre-dispatch and PASA formulation using the Murraylink dynamic rating forecast on the following two constraint equations at 1000 hrs on Wednesday 27th May 2026.

VSML_RAT_LIM_DYN
SVML_RAT_LIM_DYN

For full details on the formulation, the updated constraint equations have now been loaded into AEMO's pre-production systems.

Terry Liu
AEMO Operations

VicGrid has conducted studies and determined that the maximum generation contingency size in Victoria can be increased from 600 MW to 750 MW.

This change affects the generator limitations for prior outage conditions especially in the South-west Victoria area. The new generation limitation for outages is now 750 MW. AEMO has implemented this change in production on 13th May 2026 by updating generation constraints to increase the generation upper limits for outage conditions.

Please refer to the Network Outage Schedule for any upcoming outages in south-west Victoria here.
https://www.aemo.com.au/energy-systems/electricity/national-electricity-market-nem/data-nem/network-data/network-outage-schedule

For further details on this change please refer to VicGrid Limits Advice or contact VicGrid.
vicgrid.com.au/transmission-planning/planning-the-energy-grid

Terry Liu
AEMO Operations

AEMO and APA have been working on better ways to reflect Murraylink transfer capability more accurately during high ambient temperature conditions. APA has supplied AEMO with a real time dynamic rating and AEMO will apply this in new constraint equations to dispatch Murraylink.

At this stage, the constraint equations will only be active in Dispatch timeframe.

The following two constraint equations will be implemented in constraint set V-NIL and S-NIL, at 1000 hrs on Thursday 12th March 2026:

VSML_RAT_LIM_DYN
SVML_RAT_LIM_DYN

For full details on the formulation, the new constraint equations have now been loaded into AEMO's pre-production systems.

Terry Liu
AEMO Operations

AEMO ELECTRICITY MARKET NOTICE

The Forecast LOR3 condition in the NSW region advised in AEMO Electricity Market Notice No. 131762 is cancelled at 1040 hrs 18/12/2025

Manager NEM Real Time Operations

AEMO ELECTRICITY MARKET NOTICE

AEMO declares a Forecast LOR3 condition under clause 4.8.4(b) of the National Electricity Rules for the NSW region for the following Period:


[1.] From 1830 hrs 18/12/2025 to 1930 hrs 18/12/2025.
The maximum load (other than interruptible loads) forecast to be interrupted is 50 MW at approximately 1900 hrs.


AEMO is seeking a market response.


AEMO estimates the latest time at which it would need to intervene through an AEMO intervention event is 1300 hrs on 18/12/2025.

Manager NEM Real Time Operations

AEMO ELECTRICITY MARKET NOTICE

AEMO has conducted technical assessments to evaluate the adequacy of existing over-frequency generator shedding (OFGS) scheme in South Australia. The OFGS scheme helps to maintain frequency operating standards by tripping generators in a pre-determined manner during over-frequency conditions, to minimise the risk of cascade tripping.

AEMO?s review found that system security risks can arise when high levels of power transfer out of SA coincide with periods when the available OFGS capacity is insufficient to manage potential over-frequency conditions for a non-credible trip of the Heywood interconnector. As such a system normal constraint is required to manage the combined SA export capacity under such conditions, so as to maintain SA power system operations within the limits advised by ElectraNet.

The following constraint equation was implemented at 1425hrs 15 December 2025:
S_V_HEYWOOD_OFGS


Ben Blake
AEMO Operations

AEMO ELECTRICITY MARKET NOTICE

Transgrid has advised AEMO of an new voltage stability limit in south-west NSW for loss of Lower Tumut to Wagga (051) 330 kV line. AEMO has now completed the review and testing of this new constraint equation and will implement the following constraint equation in AEMOS Production systems at 0900hrs Monday 8th December 2025.
N::N_NIL_WGLT

This constraint equations includes the generators in southern NSW on the left-hand side as well as Murraylink and VNI.

For full details on the formulation, the new constraint equation has now been loaded into AEMO's pre-production systems.

Ben Blake
AEMO Operations

AEMO MARKET NOTICE

As a part of the 2025 Constraint Formulation Guidelines consultation the threshold for the constraint equation left-hand side (LHS) factors is changing from 0.07 to 0.15. This change becomes effective on 2nd December 2025. AEMO will implement the constraint equation changes in a staged process from 1000 to 1600 hrs on 2nd December.

Many of the constraint factor changes have already been applied to AEMO?s pre-productions systems.

For more information on the Constraint Formulation Guidelines changes see this link:
https://www.aemo.com.au/consultations/current-and-closed-consultations/isf-consultation-of-constraint-formulation-guidelines


Ben Blake
AEMO Operations