Project Specification Consultation Report – Summary
Regulatory Investment Test – Transmission – August 2026
AusNet has published a Project Specification Consultation Report (PSCR) to evaluate options to manage the risks posed by deteriorated 500kV insulators in the Gippsland region to meet AusNet’s regulatory obligations and community expectations. Publication of this PSCR represents the first step in the Regulatory Test for Transmission (RIT-T) process.
This RIT-T is part of a wider insulator replacement program. The 500kV insulators in the Gippsland region have been prioritised over other insulators in the wider insulator replacement program due to their accelerated deterioration and the timeliness to meet the investment need.
The two 500kV transmission lines from Hazelwood Terminal Station (HWTS) to South Morang Terminal Station (SMTS) (HWTS-SMTS No. 1 and HWTS-SMTS No. 2) are crucial to the secure and reliable power supply in Victoria. The insulators on these lines in the Gippsland region are exhibiting advanced corrosion, materially increasing the likelihood of failure, consistent with the insulator failure event in January 2024 on the HWTS-SMTS No. 2 line, which prompted the current targeted insulator replacement program.
These deteriorated 500kV insulators at 244 towers on the HWTS-SMTS transmission lines present credible and escalating network and public safety risk, which comprises of:
- 223 towers on HWTS-SMTS No. 2 line
- 21 towers on HWTS-SMTS No. 1 line
AusNet has identified a total of eight options to manage these risks. However, the only credible solution is to replace the insulators and thus, the following three options are considered credible:
- Option 1 – replace insulators over three years from 2027 to 2029
- Option 2 – replace insulators over five years from 2027 to 2031
- Option 3 - replace insulators over 10 years from 2027 to 2036
Given the significantly deteriorated condition of the insulators and a recent history of an insulator failure on the HWTS-SMTS No. 2 line, AusNet does not consider delaying the start of the project beyond 2027 as a credible option to meet the need in time.
AusNet also does not consider non-network solution as a credible option because the deteriorated insulators cannot be retired and non-network solution will not mitigate any of the safety, bushfire and network risks posed by the deteriorated insulators.
AusNet welcomes written feedback on this PSCR by 30th October 2026, which can be provided to [email protected]. In the subject field, please reference “Gippsland 500kV insulators PSCR”.