The publication of the Project Assessment Conclusions Report (PACR) marks the completion of the Regulatory Investment Test for Transmission (RIT-T), which evaluates options to address the condition of the towers on the Heywood Terminal Station to Alcoa Portland 500 kV Nos. 1 and 2 lines (HYTS-APD), which are at risk of failure if no remediation actions are performed. The PACR is the final stage of the RIT-T process, which has been conducted in in accordance with clause 5.16 of the National Electricity Rules (NER) and section 4.2 of the RIT-T Application Guidelines.
HYTS is located in south western Victoria and is the main terminal station interconnecting the Victorian 500 kV transmission back bone with the South Australian transmission network via a double circuit 275 kV line. HYTS also supplies the Portland aluminium smelter via a double circuit 500 kV line.
Twenty-eight towers (i.e., T597, T606 to T628B) along the 500 kV HYTS-APD line have been identified as being in poor or very poor condition. A staged replacement program is envisaged as the best way to mitigate the increasing risk of asset failure. The program will start at the end of the circuit (i.e., closest to the coast), and then progressively move inland. The first phase of the program is focused on nine towers - T628B; T628; T627; T626; T625; T624; T623; T621; and T618. A recent condition assessment survey found that these assets need ‘urgent replacement’.
The PACR has examined alternative options for addressing the nine towers, which are in poor or very poor condition. The PACR has also considered a refurbishment option, which previously was not feasible due to outage constraints.
The preferred option is to replace the nine corroded towers with new steel lattice towers. The replacement towers will be galvanised steel lattice towers that comply with current design standard AS/NZS 7000. The construction method will allow all overhead infrastructure such as the insulators, conductors and groundwires to be replaced at the same time. The scope of this option has been amended from the PADR, in which T609 was descoped and T623 was added, due to its worse structural condition, including the upgrade of 3 transmission tower footings.
The key benefit associated with the preferred option is that it removes all risks associated with the failure of degraded assets, as well as reducing the risks associated with a failure from a high intensity wind event. The direct capital cost of this option is approximately $60.18 million in nominal terms. Construction is expected to commence in January 2026 with for completion and commissioning by March 2027.
AusNet welcomes any questions on this project or feedback on the PACR, which can be provided to [email protected]. In the subject field, please reference ‘RIT-T PACR – Tower Replacement HYTS-APD.’