Transgrid PACR: Maintaining Reliable Supply to the North West Slopes area

Market Network Service Provider, National Electricity Market
StageProject Assessment Conclusions Report
ConvenorAEMO NSP
Accepting submissions?No

Transgrid has published the Project Assessment Conclusions Report (PACR) for Maintaining Reliable Supply to the North West Slopes area in Northern NSW. The PACR has been prepared as the final step in the Regulatory Investment Test for Transmission (RIT-T) process and follows the Project Assessment Draft Report (PADR) published in February 2022.

Transgrid’s latest forecasts indicate that electricity demand is expected to increase substantially in the North West Slopes area going forward due to a number of substantial industrial loads that are anticipated to connect, as well as underlying general load growth in Narrabri and Gunnedah.

Schedule 5.1.4 of the National Electricity Rules (NER) requires Transgrid to plan and design equipment for voltage control to maintain voltage levels within 10 per cent of normal voltage.  The NER also requires the power system to be operated in a satisfactory operating state, which requires voltages to be maintained within these levels, both in normal operation and following any credible contingency event.

Transgrid has undertaken planning studies that show that the current North West Slopes network will not be capable of supplying the combined increases in load in the area without breaching the NER requirements. Transgrid’s planning studies also show that the increased demand will also lead to thermal constraints going forward, particularly during times of low renewable generation dispatch in the region.

If the longer-term constraints associated with the load growth are unresolved, it could result in the interruption of a significant amount of electricity supply under both normal and contingency conditions due to the voltage and thermal limitations in the area.

In February 2022, Transgrid published the Project Assessment Draft Report (PADR) and invited written submissions on the material contained in the PADR. In response to the PADR, Transgrid received submissions from eight parties. Transgrid engaged further with parties to confirm the status and technical feasibility of the options, which involved the provision of further information from these parties. Transgrid thanks those who made a submission throughout the RIT-T process.

The assessment in this PACR finds that a non-network solution provided through a Battery Energy Storage System (BESS) at the Gunnedah 132 kV substation and the installation of a third transformer at Narrabri 132 kV substation in the near-term, along with upgrades to existing transmission lines in the longer term, is the preferred option for meeting the identified need.

In accordance with the requirements of the Rules, a summary of the Project Assessment Conclusions Report is made available on the AEMO website. A copy of the PACR can be obtained from Transgrid’s website or by emailing

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