Transgrid PACR: Maintaining reliable supply to Broken Hill

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

Transgrid has published the Project Assessment Conclusions Report (PACR) for maintaining reliable supply to Broken Hill. The PACR has been prepared as the final step in the Regulatory Investment Test for Transmission (RIT-T) process and follows the Revised Project Assessment Draft Report (PADR) published in October 2021.

Broken Hill is located in the far west of New South Wales and is part of Transgrid's south western transmission network. It is currently supplied by a single 220 kV transmission line, 'Line X2', from Buronga which spans approximately 260 km. 

When Line X2 is out of service due to a planned or unplanned outage, electricity supply to Broken Hill is supported by two diesel-fired turbines owned by Essential Energy to avoid involuntary load shedding (these turbines each have a nameplate rating of 25 MW). Transgrid relies on these diesel-fired turbines to meet the NSW Electricity Transmission Reliability and Performance Standards 2017 set by the NSW Energy Minister and regulated by the NSW Independent Pricing and Regulatory Tribunal (IPART). In accordance with these standards, Essential Energy's diesel-fired turbines allow Transgrid to operate its network so as not to expect more than 10 minutes of unserved energy (EUE) per year at average demand.

Essential Energy notified Transgrid of its decision to divest the diesel-fired turbines located at Broken Hill and that it would withdraw its provision of network support. If no action is taken by Transgrid, this will result in the required reliability of supply to Broken Hill not being maintained, and involuntary load shedding when Line X2 is on planned or unplanned outage.

Transgrid consider this a 'reliability corrective action' under the RIT-T as the identified need is to ensure that the externally-imposed reliability standards for Broken Hill continue to be met. 

In October 2022, Transgrid published a revised Project Assessment Draft Report (PADR) and invited written submissions on the material contained in the revised PADR. In response to the revised PADR, we received submissions from four parties. We engaged further with parties to confirm the status and technical feasibility of the options, which involved the provision of further information from these parties as well as technical feasibility assessments. Thank you to those who made a submission throughout the RIT-T process. 

The assessment in this PACR finds that the continued operation of the existing diesel-fired turbines as an interim measure, followed by network support provided by the Hydrostor compressed air storage solution (Option 1A(4)) is the top-ranked option. This option is expected to deliver $286 million in net benefits, which is approximately 5.8 per cent greater than the next highest option.

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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