The area of the Victorian and NSW power system bounded by Ballarat, Dederang, and Darlington Point, referred to as the ‘West Murray’ zone has attracted significant investment in grid-scale solar and wind generation, despite being a remote and electrically weak part of the NEM.
The rapid scale and pace of inverter-based renewable generator connections (refer to generation maps) has resulted in unprecedented technical issues impacting grid performance and operational stability.
The nature, extent and causes of these issues are only becoming apparent with the advanced and very 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 West Murray. Below are some of the solutions AEMO is proposing :
- Declared a system strength gap on 13 Dec 2019
- Beta testing a shareable PSCAD modelling platform
- Continue to encourage combined connections groups
- Restructure AEMO’s connection teams
- Grow AEMO’s account management capability
- Establish a well defined and transparent assessment sequence
- Develop novel technical solutions, e.g. via the Advanced System Integration Group
- Validate system model via measurements to enable operation closer to system capability
- Review ‘do no harm’ and potentially ‘open access’
- Support and lead network augmentations via the current RIT-T processes and the Integrated System
AEMO is seeking feedback from stakeholders on its proposed initiatives. Submissions should be emailed to email@example.com by Friday, 21 February 2020.
Prospective connection applicants
Developers interested in connecting generation in the West Murray and surrounding area are encouraged to contact their local network service provider (NSP) or AEMO 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:
- There will be very 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, in addition to all other 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 little or no scope to add generation to runback or inter-trip schemes.
- For projects that are able to address the technical challenges of connection, all grid-scale generation in the West Murray zone will be subject to ongoing thermal, voltage stability and system strength constraints until significant network infrastructure investments are approved and completed.
To put these network transfer constraints in perspective:
The currently identified maximum thermal network transfer limit for the West Murray region is 1,700 MW in ideal conditions. At higher temperatures, this limit will reduce. There are additional voltage stability limits on some lines and further network constraints will be applied in the near term.
Installed and commissioned generation in the West Murray zone as at February 2020 is already at 1,700 MW. There are currently around 1,200 MW of committed (pre-commissioning) inverter-based generation projects for connection in the West Murray zone and about 3,000 MW in the application phase.
Thermal and stability limits mean it will not be possible for many of these projects to connect or generate at full output ahead of significant investment in network infrastructure.
In-progress connection applications
AEMO has notified proponents that instability issues impacting the West Murray area are delaying the assessment of projects in commissioning, those waiting for registration and in application.
Detailed modelling is now absolutely essential for technical assessments in weak areas of the grid, but the level of detail inevitably makes that process slower. AEMO is dedicating significant resources to the development and testing of solutions to re-establish a stable base case on which to progress projects in the area.
The NSP facilitating the connection and AEMO will contact the proponents directly.
West Murray Technical Forum - 10 February 20201.47 MB
Infographic: Transforming Australia's energy system West Murray344.04 KB
Notice of Victorian Fault Level Shortfall at Red Cliffs375.2 KB
Power system Limitations December 2019421.25 KB
Victorian Annual Planning Report (VAPR): 20191.75 MB
About the West Murray zone
Q: Where is the West Murray zone?
The West Murray zone includes sections of the electricity transmission and distribution networks located in north-west Victoria and south-west NSW, bounded by Ballarat, Dederang, and Darlington Point. Please click here to access the West Murray map.
Q: Who operates the electricity network in the West Murray zone and what are their roles in connecting new generation?
Within the West Murray zone, Powercor and AusNet Services are the electricity distribution companies in the Victorian region and Essential Energy in NSW. AusNet Services is the main transmission network owner and operator in Victoria and TransGrid in NSW.
As the service provider for the shared transmission network in Victoria, AEMO is responsible for managing the process for connecting generation to the high voltage network. TransGrid performs this role for transmission in NSW and the distribution businesses manage connections to their own networks. AEMO is also the Victorian transmission planner, using available information from infrastructure owners, investors and demand trends to identify when and where new transmission network infrastructure should be built. With some limited exceptions, assessments must be based on an economic business case where benefits exceed development costs.
Across the NEM, AEMO’s role as market and system operator involves assessing standards and remediation proposals for connecting plant that could affect power system security. AEMO has advisory and approval functions at various stages of the connection, registration and commissioning process in all regions.
Q: What is AEMO's role with generators wanting to connect in Victoria?
Following the privatisation of Victoria’s electricity sector (generation through to retail) in the 1990s, the role of transmission planner has been managed by an independent authority, initially the Victorian Energy Networks Corporation (VENCorp) and then AEMO from 2009.
As Victoria’s transmission network planner, AEMO is responsible for the planning of the Victorian transmission network. AEMO uses available information from infrastructure owners, investors and demand trends to make decisions on when and where new transmission network infrastructure should be built, or services obtained to support the network. Most significant investments must satisfy an economic business case where benefits must exceed development costs.
Where AEMO assesses that transmission network or non-network development is needed and economically justified, augmentation projects may be competitively tendered if they can be owned and operated independently of existing network infrastructure.
Click here for more information.
Q: Has there been a substantial change in new generation sources in the West Murray zone in the last few years?
This area has seen a substantial increase in inverter-based generation, mostly grid-scale solar farms particularly in the last three years.
In addition to the 1,700 MW of installed wind and solar generation in the West Murray zone as at February 2020, around 600 MW are at various stages of commissioning and further projects totalling about 2,300 MW are committed. Many more remain in the application phase.
There are no significant conventional synchronous generators in the West Murray zone or for several hundred kilometres.
Issues in the West Murray zone
Q: What are the issues impacting the electricity network and generators in West Murray?
The scale and pace of new inverter-based generation connected in electrically remote and weak areas of the National Electricity Market is presenting unprecedented technical issues affecting power system security and stability in those areas.
This is the case in the West Murray zone with significant investment in new generation into a low system strength network that is a long distance from major energy usage areas and ‘synchronous’ machines that provide critical system strength services. A minimum level of system strength is required for the power system to remain stable under normal conditions and to return to a steady state condition following a system disturbance.
Further, the transmission infrastructure in this part of the network is subject to thermal and voltage stability constraints, restricting the generation output that can be transferred across this part of the network.
Both the system strength and constraint issues are exacerbated as the number of inverter-based generation connections increase along these lines.
In September 2019, AEMO identified that five solar farms in the West Murray zone produced voltage ‘oscillations’ following a transmission line fault, which exceeded the regulated limits for power system security.
Q: When did AEMO become aware of these issues?
The challenges associated with the West Murray zone being a remote and electrically weak part of the NEM has been publicised over the last few years, including AEMO’s 2016 Victorian Annual Planning Report and the 2018 Integrated System Plan (ISP). Generation maps are also publicly available to facilitate informed investment decisions.
AEMO first published information for Victorian transmission network connection applicants about the impact of thermal limits in the area in late 2015, with multiple updates over time as conditions have changed.
The full extent and causes of the interactions between inverter-based generation as they respond to system disturbances are still emerging. These phenomena have become apparent as the capability has become available for AEMO to develop detailed PSCAD® models extending over a wide area of the network. This phenomenon would not have been uncovered by conventional power system simulation tools used worldwide. It is now possible for detailed analysis of actual system events to be performed and for connection studies to capture potential interactions that may occur with network and inverter-connected plant. Tests performed in late 2019 have confirmed these interactions are occurring in the West Murray zone. They are at the heart of the network constraints that AEMO introduced in September 2019 restricting the output of five constrained solar farms to maintain post-fault stability within regulated power system security limits.
AEMO has not only been working with the impacted solar farms, network service providers and the equipment manufacturer to identify and implement acceptable solutions, but also communicating and engaging with committed and prospective generators in the area directly via email and calls, along with reports, a technical forum and through our AEMO Communications eNewsletter.
Q: Why did AEMO constrain the five solar farms?
As the market and system operator of the NEM, AEMO needed to constrain the output of these solar farms to a level at which it could be satisfied that the integrity of the electricity system would be protected. AEMO’s responsibility for power system security means it must take all available steps to keep the power system within operating limits, both in normal operation and immediately after a credible fault or event that could occur on the power system at any time.
Q: How are current and prospective generators in West Murray impacted?
AEMO has been working closely with the solar generators, their equipment suppliers and network service providers (Powercor and TransGrid), to help develop a solution that would restore operational compliance.
The generators and network service providers now need to complete a regulated process to agree and verify the necessary changes, with AEMO’s approval. However, in these network conditions every adjustment has consequences for generator and system performance, some unforeseen. As a result, regrettably this assessment has been a slow process.
Once tested and implemented, the solution will enable NSPs and AEMO to resume assessments of commissioning and committed generation projects in the West Murray zone. These will need to be conducted sequentially to meet power system security needs.
Q: Do these issues risk the delayed registration/constraints for neighbouring projects around the WMZ?
AEMO and the NSPs will continue with the connection and registration process for projects that are not considered to be within the West Murray Zone. Normal operational constraints will still apply to all regions.
Q: Will AEMO share the contingency events and network conditions for the assessment of each project with all participants?
No, AEMO intends to discuss the contingency events and network conditions with each proponent for its own project.
Q: Are these issues unique to West Murray or do they relate to the rest of the National Electricity Market?
The issue observed in West Murray are unique to the particular electrical topology of the zone. However, there are emerging challenges across the NEM in areas of low system strength and high concentration of inverter-based generation.
Q: What is AEMO doing to manage these issues?
AEMO is working closely with industry to evolve the power system through solutions that maintain power system security and deliver reliable and affordable energy to consumers.
Specific to the oscillation issues, AEMO has been working closely with the solar generators, their equipment supplier and network service providers (Powercor and TransGrid), to help develop solutions that would restore operational compliance. Once tested and implemented, the solution will enable NSPs and AEMO to resume assessments of commissioning and committed generation projects in the West Murray zone. These will need to be conducted sequentially to meet power system security needs.
Regarding the low system strength in West Murray, AEMO declared fault level shortfall of 312 MVA at the Red Cliffs fault level node in December 2019 and is in the process of procuring services to fill the shortfall by 1 January 2021 (refer to the Notice of Victorian fault level shortfall at Red Cliffs report).
This is the third system strength gap identified for the NEM under AEMO’s system strength requirements methodology, following South Australia and Tasmania in October 2017 and November 2019, respectively.
To address network congestion, alleviate thermal constraints and improve the power transfer capability from the West Murray area, AEMO is implementing a transmission infrastructure augmentation plan as outlined in our latest Integrated System Plan (ISP) and Victorian Annual Planning Report.
Two major interconnector projects that would deliver these benefits for the West Murray area:
- Project EnergyConnect: a new interconnector between South Australia and NSW, likely to be delivered within the next five years.
- VNI West (formerly “Keranglink”): a longer-term project to add an interconnector between Victoria and New South Wales.
In addition, the Western Victoria Renewable Integration project aims to address current limitations in the Western Victoria transmission network.
For further information on the ongoing and completed transmission augmentation projects, please visit AEMO’s website.
Q: What does this mean for the current connections process with AEMO and network service providers?
The operational generators that are currently constrained and network service providers now need to complete a regulated process to agree and verify the necessary changes, with AEMO’s approval. However, in these network conditions every adjustment has consequences for generator and system performance, some unforeseen. As a result, regrettably this assessment has been a slow process.
Q: Can you explain AEMO's proposed sequencing approach?
Due to the large number of projects that are in commissioning and awaiting registration, the following process has been proposed in order to connect the backlog of projects in a way that maintains a secure operating state as required by the National Electricity Rules.
AEMO proposes that projects will be grouped as follows and, once acceptable performance and models have been re-established for the constrained generation, the place order will be via date (earliest first, subject to meeting all pre-assessment conditions as noted above). If any of the dates for projects within group 2 or 3 are the same, then the date of registration will determine priority order.
Group 1: Constrained – commissioning: date of request for approval to proceed to next hold point
Group 2: Registered: date of registration
Group 3: Committed (Connection Agreement and 5.3.4A/B): latest of connection agreement date, 5.3.4A approval or 5.3.4B approval.
AEMO sought feedback from attendees at the WM Forum on 10 February 2020 about the sequencing proposal.
Q: How will I know where my project is in the proposed sequencing timeline?
Proponents who currently have a committed, registered or commissioning project in the West Murray Zone will be contacted directly to discuss the assessment approach and sequencing timeline.
AEMO is committed to regular progress reports as we work towards removing constraints and progressing new connections in West Murray.
Q: Will AEMO release further information on feedback from the industry in overcoming these issues?
AEMO has requested feedback from the industry by 21 February and will provide an update shortly afterwards.