West Murray


The West Murray Zone is an area of the National Electricity Market (NEM) with low system strength, extending across parts of Victoria and New South Wales. This area has attracted significant investment in grid-scale solar and wind generation in the past three years. The scale and rapid pace of inverter-based renewable generator connections has resulted in new technical challenges, impacting grid performance and operational stability.

The nature, extent and causes of these issues only become apparent with the advanced and detailed modelling capability that is now essential for technical assessments in weak areas of the grid.

AEMO is committed to working collaboratively and transparently to find solutions to the challenges presented in the West Murray Zone. This includes working closely with developers, generators, network service providers, equipment manufacturers and industry groups.

These solutions and milestones include:

AEMO is also working on long-term solutions:

  • Develop novel technical solutions to reduce interactions causing system instability, e.g. via the Advanced System Integration Group
  • Ongoing validation of system model against measured event data to enable operation closer to system capability
  • Review the regulated connections process to facilitate coordinated assessment of multiple connection projects that may impact each other.
  • Support and lead network augmentations via the current Regulated Investment Test for Transmission (RIT-T) processes and the Integrated System Plan

Current and prospective connection applicants

Developers interested in connecting generation in the West Murray Zone and surrounding area should contact their local network service provider (NSP) before making any financial commitments, to discuss whether, when and how they might be able to progress their project.

Prospective developers and current applicants should be aware of the following:

  • The capacity of the existing network in the WMZ to host large scale inverter-connected generation has likely been reached, or will be reached by the time already-committed projects are integrated. New and existing generation across large parts of the WMZ will be materially constrained for significant periods of time pending large-scale network investment. This will not only restrict commercial output, but may prevent or delay completion of commissioning for new projects.
  • Connections that rely on future regulated upgrades to the network cannot be assessed until those upgrades are substantially complete.
  • There will be significant delays in NSP and AEMO project assessments due to the complexity and detail of studies required to confirm the impact of a new connection on system security and quality of supply.
  • Very low system strength increases the potential for interaction of inverter-based resources to produce unacceptable voltage oscillations. For system security reasons, any proposed generating plant that is shown to contribute to instability will not be connected.
  • AEMO and NSPs will not be able to progress any assessment of proposed performance standards without a complete, site-specific PSCAD model, incorporating all information required by AEMO’s Power System Model Guidelines.
  • A full system strength impact assessment will be required for all new and modified connections proposed. System strength connection works or remediation schemes will be needed, which will require additional capital investment – there is no scope to add generation runback or inter-trip schemes.

Intermittent Power System Oscillations Update - April 2022

AEMO has observed intermittent power system oscillations in the West Murray area (VIC/NSW) under a variety of conditions since first identified on 20 August 2020, following a line trip in the West Murray Zone.

Soon after the event AEMO developed a bespoke tool that monitors high resolution power system quantities at Red Cliffs Terminal Station (RCTS) 220 kV and captures intervals with sub-synchronous voltage oscillations.

The frequency of oscillations has been around 19 Hz with varying magnitude. While analysing number of instances when power system oscillations were observed the highest magnitude of oscillations has been closer to the Red Cliffs area. 

On 25 August 2021, AEMO held an industry briefing where we presented information regarding a number of instances of these oscillations. Subsequent to that AEMO also released sample oscillations data for stakeholders to analyse.  

AEMO is working closely with AusNet, Powercor and relevant participants to resolve the issue. AusNet installed additional CT-Labs1 monitoring equipment at Wemen area which is helping the investigation. Powercor has now installed similar monitoring equipment in their sub-transmission network under Wemen Terminal Station to further support the investigation.  

AEMO in collaboration with AusNet and Powercor is currently developing a report that will provide further information on the observed intermittent power system oscillations. The report is expected to be published in Quarter 3 of 2022.

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