Overview

Line 86 is a 330 kV single-circuit transmission line, running between Tamworth and Armidale (111 km), and was constructed in 1982 using mostly composite wood pole (two piece wood pole) structures.   Line 86 is the only 330 kV line in our network that was not constructed using steel towers. The unique construction of this transmission line means that wood rot beneath the composite pole joint sleeve is prevalent throughout the composite wood poles that are utilised along the line.

Transgrid is applying the Regulatory Investment Test for Transmission (RIT-T) to options for managing risk on Line 86 (Tamworth-Armidale). This would involve replacing existing transmission infrastructure to address condition issues with options which also have the potential to provide additional wider wholesale market benefits.

RIT-T process and submissions

Transgrid must show that the preferred option for managing risk on Line 86 will deliver the greatest net benefits to energy consumers. The net benefits delivered by the project are assessed using the Regulatory Investment Test for Transmission (RIT-T) administered by the Australian Energy Regulator (AER).

The RIT-T assesses network and non-network solution options from a technical and economic perspective by:

  • Informing stakeholders of the investment need and proposed options to address this need
  • Testing the market for alternative and more efficient solutions
  • Explaining to stakeholders the basis on which the preferred option has been selected.

We have now completed the final stage of the RIT-T and after assessing multiple options, identified that a focused replacement of the highest risk Line 86 wood poles, like for like and in-situ with concrete or steel poles is considered to maximise the net benefits and satisfy the RIT-T.

Project Specification Consultation Report

In December 2021 we published a Project Specification Consultation Report (PSCR), the first step in the RIT-T process.

The PSCR detailed the need to manage risk on Line 86 and describes credible options to meet the need, including technical characteristics that would be required of a non-network option.

We received submissions from three parties in response to the PSCR. All parties that submitted to the PSCR requested confidentiality, therefore we have not reproduced any of their material on our website.

Project Assessment Draft Report

The Project Assessment Draft Report (PADR), published in May 2022, provides transparency into the considerations for investment options to manage risk on Line 86, and the associated market benefits. A key purpose of this PADR, and the RIT-T more broadly, is to provide interested stakeholders the opportunity to review the analysis and assumptions, provide input to the process, and have certainty and confidence that the preferred option has been robustly identified as optimal.

Submissions received in response to the PSCR were considered when preparing the PADR.  The PADR includes a full quantitative analysis of the proposed options and expected net market benefit across a range of scenarios and sensitivities. We have published the following supporting documents: 

We invited written submissions on the material contained in the PADR. We did not receive any submissions in response to the PADR.

Thank you to those who made a submission throughout the RIT-T process.

Project Assessment Conclusions Report

In July 2022, we have published the Project Assessment Conclusions Report (PACR) for Managing Risk on Line 86.

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 May 2022.

The assessment in this PACR finds that a focused replacement of the highest risk Line 86 wood poles, like for like and in-situ with concrete or steel poles is the preferred option for meeting the identified need.

PACR Supporting Documents

If you have any questions about the project, please contact network.solutions@transgrid.com.au or phone 1800 222 537.