State of the System update

10 min

Welcome to AEMO’s fifth State of the System update, a regular round-up of developments in the east coast energy system. Its aim is to provide updates, build awareness of emerging issues and highlight engagement opportunities on important initiatives and consultations.

As always, we welcome feedback via or through our survey and encourage anyone who is interested in receiving future updates to subscribe.

NEM connections update

Financial Year 2021

The development of renewable generators remained strong between July 2020 and June 2021. In total there were 33 generators totaling 2.68 GW registered and 16 generators totaling 1.73 GW commissioned in the NEM. This represents an increase of 600 MW registered and 480 MW commissioned compared to the previous financial year.

Further, 18 projects with a total capacity of 2.1 GW became committed after successfully completing the first stage of the connection process. There was a decline of 1.49 GW in committed generation compared to the prior financial year.

Highlights of Q3, 2021 – to date

Since 1 July 2021, 6 new generators with a total capacity of 953 megawatts (MW) achieved registration:

  • Wandoan Battery Energy Storage (QLD/100 MW)
  • Victorian Big Battery (VIC/300 MW)
  • Stockyard Hill Wind Farm (VIC/286 MW)
  • Bulgana Green Power Hub (VIC/104 MW) (capacity increase from 100 MW to 204 MW)
  • Suntop Solar Farm (NSW/150 MW)
  • Mannum-Adelaide Pipeline Pumping Station No 2, PV Units 1-6 (SA/13 MW)

The NEM generation maps are available here and will be updated by the first week of October 2021. 

Final incident report - trip of multiple generators and lines in QLD and associated under-frequency load shedding

In October, AEMO published the final incident report for the major system incident that occurred on 25 May 2021 in QLD.

AEMO’s investigation has identified that a loss of DC and AC auxiliary supplies at Callide C4 Power Station at 1333 hrs led to this unit motoring for over 32 minutes. During the motoring period Callide C3 and Callide B2 units also tripped. At 1406 hrs, the situation at Callide C4 developed into a 2 phase electrical fault. This was subsequently cleared from the power system through remote end tripping of all circuits connecting Calvale 275 kV substation to the system. Following the fault at Callide C4, multiple events occurred in quick succession negatively impacting the power system. A summary of the key impacts of this incident is included below:

  • A total of 3,045 MW of scheduled generation and approximately 408 MW of DPV generation disconnected
  • A reduction in operational demand of approximately 2,276 MW in QLD and 25 MW in NSW
  • QNI trip leading to temporary synchronous separation of QLD from the rest of the NEM (QNI successfully reclosed after approximately 16 seconds)
  • Operation of under-frequency load shedding relays in response to low frequency in QLD
  • Forecast Lack Of Reserve (LOR)1, LOR2 and LOR3 conditions and actual LOR2 conditions in QLD

For full details of this incident and AEMO’s findings and recommendations please see the final report here.

Synchronous condensers testing on track

To fill the declared system strength gap in South Australia, ElectraNet is in the process of commissioning four large synchronous condensers, two at Davenport and two at Robertstown. Once commissioned, AEMO will commence transitioning to new limits and generator combinations.

The Davenport synchronous condensers were energised and completed testing in the first week of August 2021 and have been operational for a few weeks. The Robertstown synchronous condensers have completed testing. ElectraNet is currently preparing for system tests.

AEMO and ElectraNet have conducted analysis to identify the impacts of these synchronous condensers on the system strength limit. It has been identified that higher asynchronous generation can be supported with these synchronous condensers in service, and that it will reduce the number of synchronous generators that are required to be online.

Transition to new limits/generator combinations

Transitioning to the new limits for the synchronous condensers online is a three-stage process.

  • Stage 1: plant commissioning tests.
  • Stage 2: 2 to 4 week monitoring period. If no issues are observed starting at 2 weeks, AEMO will progressively lift the constraint on asynchronous generation in SA.
  • Stage 3: 6 to 12 week extended monitoring period after Stage 1.This stage is to transition to a minimum of two synchronous generators on-line.

During this monitoring period, if AEMO is not satisfied with the performance of the synchronous condensers, AEMO may extend this monitoring period and limit asynchronous generation in SA.

Further information

Prior to each change to limits or generator combinations, AEMO will inform the market via a market notice.

The limits advice is available on the Congestion Information Resource limits advice page. Once the synchronous condensers are commissioned outages will be notified via the Network Outage Schedule (NOS) and constraints implemented as required. Keep updated on AEMO's website here.

Power system oscillations

AEMO has observed intermittent power system oscillations in the West Murray Zone (Vic/NSW) for the past year. The oscillations have been observed under system normal conditions as well as during outages. The frequency of oscillations is around ~17 Hz and the magnitude is generally low. More recently, AEMO has observed higher magnitude of oscillations with peak-to-peak magnitude ranging from 0.5% to 2%. While there is no immediate cause for power system security or performance concern, this phenomenon may be caused by number of factors. AEMO is actively monitoring this area and engaging with network service providers, generators and the broader power system engineering community to identify and where possible resolve the causes.

On 25 August 2021, AEMO held an forum to update industry regarding this observation. Following an industry brief, as per request from the stakeholders, AEMO published some data for stakeholders to analyse.

For more information please visit AEMO's website.

West Murray Zone update

Since the last WMZ update in July’s State of the System Newsletter, three projects have completed their WMZ Integration Assessment with 5.3.4A letters being issued. In addition to this, two projects have reached committed status.

  • Yanco Solar Farm in NSW, connecting to the TransGrid network.
  • Wunghnu Solar Farm in VIC connecting to the Powercor network.

Two projects are undergoing integration assessment and AEMO is working closely with the respective NSPs on a further five projects nearing integration assessment.

Connecting projects within the WMZ remains challenging in terms of capacity. If you are still planning on moving forward with your project, please ensure you are working closely with your respective NSP and are completing all the requirements needed and as outlined in AEMO’s Connecting generators in the West Murray Zone – sequencing uncommitted projects. Whilst AEMO's National Connections team remain committed to working with all NSPs and developers who want to progress a projects in the WMZ, it remains important that developers in the application and enquiry phase continue to work with the relevant NSP to understand potential impacts on their project.

If you are unsure if your project is in the WMZ, please see the WMZ map on the AEMO website here or alternatively, please contact your connecting NSP.

Western Victoria Connections: Industry fact sheet

AEMO’s Victorian Connections team has released its updated Q&A: Connections to the Western Victoria transmission network, representing the Victorian part of the West Murray Zone. It explains the multiple challenges around system constraints, system strength and MLFs. Whilst there are various initiatives underway by AEMO, the Victorian Government and the industry to lessen the impacts of these issues, connections in this area are expected to remain very challenging.

NEM registration documentation updates for small battery systems

AEMO has recently updated its Guide to Generator Exemptions and Classification of Generating Units in relation to small battery systems, with a nameplate rating of less than 5 MW. The guide now clarifies the circumstances when the electricity consumed from the gird to charge a small battery system intended for subsequent energy production, is treated as a ‘market load’ or ‘auxiliary load’. The guide has also been updated to clarify a person who owns, controls or operates a generating system with a total nameplate rating of at least 5 MW but less than 30 MW, that comprises of a small battery system with a nameplate rating of less than 5 MW, may apply to AEMO for an exemption from the requirement to register as a generator and the guide now uses the term 'battery system' in place of 'battery storage facility'.

In line with these guide amendments, the Registering a Battery System in the NEM – Fact Sheet has been updated and now further outlines AEMO's approach to registration of battery systems and the classification of their connection points in the NEM.

For more information about these document amendments please contact AEMO's Registration team via

NEM Engineering Framework

The Engineering Framework is a toolkit to define the full range of operational, technical and engineering requirements needed to deliver the futures envisaged by the Integrated System Plan (ISP). The framework seeks to facilitate an orderly transition to a secure and efficient future NEM system.

As part of the framework, AEMO released the Operational Conditions Summary in July. Operational conditions are generation mix and loading combinations projected to occur five to 10 years in the future that will necessitate changes to current operational practices.

The Engineering Framework will be used to develop a prioritised roadmap of actions needed to prepare the NEM for operation under the six identified operational conditions, including operation with 100% instantaneous penetrations of renewable energy by 2025.

To inform the development of this roadmap, AEMO is now working with stakeholders to define critical gaps between the work in progress and what will be needed to fully prepare for these operational conditions. A stakeholder information session will be held on 22 October 2021 to inform stakeholders of priority gaps, and present early concepts for the roadmap due for publication in December.

Please register your interest to attend the 22 October session here.

AEMO and ARENA collaborate on Connections Simulation Tool project

The Connections Simulation Tool is a joint AEMO ARENA initiative, announced by Minister Taylor in August.

A world first, the Connections Simulation Tool will provide developers, Original Equipment Manufacturers (OEMs), Network Service Providers (NSPs), and consultants with a unique opportunity to streamline the approval of connection applications. This optional service enables the use of wide-area models, aligned to those used within AEMO. Simulations run by the applicant will show the network impacts of the prospective generator when connected to the NEM.

Utilising a full power system model will provide applicants data and insights that will allow proponents and OEM’s to improve the quality of their generator models potentially reducing the need for submission iterations to the NSP and AEMO as their Connection Application progresses.

AEMO will work transparently with industry, engage with trial users, and incorporate stakeholder feedback at each stage. The first major release of the project is expected within the year.

The Connections Simulation Tool is part of a larger AEMO initiative that will also introduce HYPERSIM to support AEMO operations. For more information or to get involved please check out the AEMO website, or contact AEMO via

Connections Reform Initiative update

The Connections Reform Initiative (CRI) is in full swing and continues to host a number of workshops, following two directions webinars during early September.

The next step is the publication of a CRI Roadmap in November. This living document will provide clear recommendations to guide and drive implementation activity. There will be a public launch of this document, so watch the usual channels including AEMO Communications for that. More information is available on AEMO's website.

Subscribe to the AEMO communications newsletter here.

Integrated System Planning (ISP) update

AEMO is currently conducting modelling as part of the preparation of the Draft 2022 ISP, to be published on 10 December 2021.

The modelling is using AEMO’s 2021 Inputs, Assumptions and Scenarios Report for planning and forecasting, which are available here.

During October, AEMO will conduct stakeholder consultation on the calculation of wholesale competition benefits arising from new transmission investments. Details of that consultation will be sent to the ISP mailing list, which stakeholders can sign up to here.

2021 Electricity Statement of Opportunities

On 31 August 2021, AEMO published the 2021 Electricity Statement of Opportunities (ESOO). The 2021 ESOO presents AEMO’s outlook of supply adequacy to 2030–31.

A key focus of this year’s ESOO is on managing an accelerated transition towards high instantaneous penetration of renewable generation, thermal generation withdrawal, and ‘green’ hydrogen consumption.

Read 2021 ESOO here or visit the NEM Electricity Statement of Opportunities (ESOO) page on AEMO’s website.

Upcoming Energy Education courses

Due to ongoing demand, more course dates are now available for the National Electricity Market (NEM) Overview course. Hosted by AEMO’s inhouse subject matter experts, this valuable introductory course explores how the NEM operates as a physical power system and a wholesale market for electricity. The course is held over two half-day sessions in the same week.

For information on upcoming courses, click the links provided in the calendar below or visit the AEMO Energy Education courses webpage. Enrol via the AEMO Learning Academy or please contact for enquiries.

Please note, AEMO’s Energy Education instructor-led courses continue to be delivered in settings that comply with Covid-19 safety requirements. Some courses on the Wholesale Electricity Market (WEM) will now be delivered in-person, but will remain subject to any change in restrictions – further details are on the AEMO Learning Academy.

Useful resources

To follow the latest news and updates from AEMO you can subscribe to a number of our newsletters on our subscribe page, or check out our newsroom.  

Latest publications:

  1. 2021 Electricity Statement of Opportunities
  2. Quarterly Energy Dynamics - Q2 2021

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