Corrective actions to continue to address the risk of insulator failure along multiple Extra-High Voltage (EHV) circuits through a risk-based replacement program.

Market Network Service Provider
StageProject Assessment Draft Report
ConvenorAEMO NSP
Accepting submissions?Yes
Submissions close03/11/2023

Project Assessment Draft Report – Summary

Regulatory Investment Test – Transmission – September 2023

AusNet is undertaking this Regulatory Investment Test for Transmission (RIT-T) to evaluate options to apply corrective actions to maintain reliable transmission network services along multiple Extra-High Voltage (EHV) circuits.

Publication of this Project Assessment Draft Report (PADR) represents the second step in the RIT-T process in accordance with clause 5.16 of the National Electricity Rules (NER) and section 4.2 of the RIT-T Application Guidelines.

This PADR sets out the detailed cost-benefit analysis of the credible options for addressing the identified need. The analysis confirms the provisional findings in our PSCR that Option 1 is strongly preferred to Option 2. At this stage, Phase Two of Option 1 has not yet been scoped or costed.

In summary, the preferred option is to 

  • Replace to 773 insulator strings from 107 transmission tower-circuits in the transmission network, including the installation of approximately 3,000 vibration dampers on the phase conductors.
  • Of the 733 insulators, 341 insulators are classified as being in Condition 5 and 432 insulator strings are classified as being in Condition 4.

This option addresses the identified need and provides an efficient, targeted replacement. At this stage, we propose to commence the works in November 2023 for completion in December 2024. 

The analysis presented in this PADR complies with the AER’s RIT-T guidelines.

Stakeholder submissions, feedback or questions are invited by 3 November 2023 to  In the subject field, please reference ‘RIT-T PADR Transmission Line Insulator Replacement.’

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