TransGrid has recently published a Project Assessment Draft Report (PADR) for improving stability in south-western NSW.
The main power system in south-western NSW consists primarily of one 330 kV transmission line from Darlington Point to Wagga Wagga (Line 63) and 220 kV transmission lines west of Darlington Point (including Line X5). Smaller underlying 132 kV transmission lines supply regional towns.
This area has seen significant growth in renewable connections to the transmission network as part of the wider energy market transition. Approximately 594 MW of renewable generation has connected in the area since December 2015 and approximately 695 MW of renewable generation is currently being commissioned. This is having an impact on how this part of the power system operates. In particular, while power has historically primarily flowed west from Darlington Point to supply rural and mine loads, this is expected to reverse with the increase in renewable generation in the area, particularly during daytime when there is an abundance of solar generation.
These changes in power flows are expected to lead to an increasing risk of power system instability going forward. Currently the only way of managing this risk is to constrain generation in south-western NSW. In recognition of the risks to future power system stability, in May 2020, AEMO implemented an operational constraint in the NEM Dispatch Engine to limit power flows and prevent this occurring.
TransGrid have identified the opportunity to strengthen the transmission network to relieve this constraint and provide market benefits to the National Electricity Market (NEM). This RIT-T has therefore been initiated to progress and consult on the assessment of investment options and whether the market benefits outweigh the costs of the investments. The investments considered in this RIT-T did not form part of AEMO’s final 2020 Integrated System Plan (ISP), and so are being progressed outside of the ISP framework.
TransGrid’s revenue determination for the 2018-2023 regulatory control period includes a contingent project for providing stability in south-west NSW (‘the Support South Western NSW for Renewables’ contingent project). This contingent project is to reinforce the transmission network in the area to enable additional renewable generation and provide net market benefits to NSW as well as the wider NEM.
Stakeholder consultation on the PSCR has assisted with developing and refining the credible options put forward in the PSCR. Specifically, consultation with third parties since the PSCR has enabled this PADR to assess the following five types of credible options:
- Option 1 – a new or rebuilt 330 kV transmission line between Darlington Point and the new Dinawan substation being constructed for EnergyConnect:
- Option 1A (new line);
- Option 1B (rebuilt line);
- Option 2 – a new 330 kV transmission line between Darlington Point and the Wagga Wagga substation;
- Option 3 – a static synchronous compensator (STATCOM) solution at the Darlington Point substation;
- Option 4 – Option 1A plus an interim 3-year battery solution; and
- Option 5 – a standalone long-term battery solution.
The PADR analysis finds that Option 1A, a new Darlington Point to Dinawan 330 kV transmission line, provides the greatest net benefits of all options and is the preferred option at this draft stage of the RIT-T.
The findings of this PADR align with the NSW Electricity Infrastructure Roadmap, which was legislated in December 2020, and will allow for more renewable energy to be dispatched into the NEM from the proposed South West NSW REZ.
TransGrid welcomes written submissions on materials contained in the PADR. Submissions are due on 5 November 2021.
In accordance with the requirements of the Rules, a summary of the PADR is made available on the AEMO website. A copy of the PADR can be obtained from TransGrid’s website or by emailing regulatory.consultation@transgrid.com.au