Transgrid Project Assessment Conclusions Report: Managing risk on Lines 21, 22, 959 & 92Z (conductor condition)

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

Transgrid has published the Project Assessment Conclusions Report (PACR) to assess options for remediating deteriorating conductor condition on four transmission lines in the Transgrid overhead transmission network (Line 21, Line 22, Line 959 and Line 92Z). The PACR is the final step in the Regulatory Investment Test for Transmission (RIT-T) process and follows the Project Specification Consultation Report (PSCR) published in February 2024.

Transgrid’s overhead transmission network contains sections where the condition of conductors is deteriorating such that they have reached, or are close to reaching, end of life. The deteriorated condition of conductors can be caused by a variety of mechanisms such as:

  • annealing due to bushfire exposure;
  • corrosion initiated by bushfire exposure; and
  • corrosion at mid-span joint locations.

Transgrid has undertaken analysis of conductor condition and deterioration mechanisms across its network, which identified approximately 1,100 km circuit length of conductors that have condition issues that require attention.

If action is not taken, the conductor deterioration is expected to lead to an increasing level of risk going forward, as the likelihood of failure increases. There are safety and bushfire risks under the ‘do nothing’ base case, as well as higher expected costs associated with reactive maintenance that may be required under emergency conditions (‘financial risk’). The proposed investment will enable us to manage safety, bushfire and financial risks on the affected lines.

We manage and mitigate safety and environmental risk to ensure they are below risk tolerance levels or ‘As Low As Reasonably Practicable’ (‘ALARP’), in accordance with our obligations under the New South Wales Electricity Supply (Safety and Network Management) Regulation 2014 and our Electricity Network Safety Management System (ENSMS).

Transgrid published a Project Specification Consultation Report (PSCR) for managing risk on Lines 21, 22, 959, 92Z (conductor condition) in February 2024. In the PSCR Transgrid presented one credible network option that would meet the identified need from a technical, commercial, and project delivery perspective. Option 1 involves targeted replacement of existing conductors along Line 21 (Tuggerah-Sydney North), Line 22 (Vales Point-Sydney North), Line 959 (Sydney North-Sydney East) and Line 92Z (Sydney North-Sydney East).

No submissions were received in response to the PSCR during the consultation period which closed in May 2024 and no additional credible options have been identified.

The assessment in this PACR finds that Option 1 is the preferred option to meet the identified need at this stage of the RIT-T.

The estimated capital cost of this option is approximately $36.6 million ($2023-24) +/- 25 per cent. Transgrid is the proponent of the proposed network project.

In accordance with the requirements of the Rules, a summary of the PACR 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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