TransGrid PACR: Managing safety and environmental risks on Line 21 (Tuggerah – Sydney North)

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

Transgrid has recently published a Project Assessment Conclusions Report (PACR) for managing safety and environmental risks on Line 21 (Tuggerah – Sydney North). 

Spanning a route of 65 km, Line 21 is a 330 kV transmission line that runs between Tuggerah and Sydney North substations. It was originally built in 1959 as part of a double circuit 132 kV line from Sydney North to Dora Creek, but was upgraded to single circuit 330 kV and turned in to Munmorah in 1962, and a tee to Tuggerah added in 1986 at Sterland. This RIT-T is being undertaken to address environmental and safety risks on a portion of this original section of Line 21 – between the Tuggerah cut-in and Sydney North substation. This section of the line is comprised of 113 steel towers and spans approximately 51 km.

Line 21 is a key link between the Central Coast and Sydney metropolitan area and will continue to play a central role in supporting the flow of energy to take advantage of naturally-diverse weather patterns, and in the safe and reliable operation of the power system throughout and after the transition to a low-carbon electricity future.

Condition issues that will impact the safe and reliable operation of the network have been found on Line 24. The condition issues raise a number of risks associated with asset failure, including safety and environmental (bushfire) risks. Investment to address the deterioration of the assets along Line 24 due to corrosion is needed to mitigate risks to safety and the environment.

Transgrid manages and mitigates bushfire and safety risks to ensure they are below tolerance levels or ‘As Low As Reasonably Practicable’ (‘ALARP’), in accordance with Transgrid’s obligations under the New South Wales Electricity Supply (Safety and Network Management) Regulation 2014 and Transgrid’s Electricity Network Safety Management System (ENSMS). The proposed investment will enable TransGrid to continue to manage and operate this part of the network to a safety and risk mitigation level of ALARP. Consequently, it is considered a reliability corrective action under the RIT-T.

Transgrid published a Project Specification Consultation Report (PSCR) for managing safety and environmental risks on Line 21 (Tuggerah – Sydney North) in July 2021. 

Transgrid put forward for consideration one technically and commercially feasible option: refurbishing the existing line by remediating or replacing the identified components. This option (Option 1) involves the refurbishment of Line 21 including replacement of asset components, earthwire, remediation of steelwork and foundations.

The primary driver for the identified need is to mitigate bushfire and safety risks associated with condition issues on Line 21 caused by corrosion. Two other options to address the need were considered but were not progressed further as they were determined technically or commercially non-feasible when assessed against the preferred option. 

No submissions were received in response to the PSCR during the consultation period which closed in October 2021 and no additional credible options have been identified.

Since the time the PSCR was published, the cost estimate factors for Option 1 have been adjusted to reflect the latest estimated resourcing requirements to implement the preferred option. This resulted in a decrease to the total cost estimate from $19.6m to $16.7m. Transgrid also adjusted the phasing of risk cost benefits to align with the Option 1 commissioning timeframe. The outcome of these updates had no impact on the ranking of the options. 

Option 1 (line refurbishment) remains the preferred option at this stage of the RIT-T process. This option is estimated to have a capital cost of $16.7 million +/- 25% and is expected to be completed by 2022/23. Transgrid is the proponent of the proposed network project.

In accordance with the requirements of the National Electricity 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

Cookies help us improve your website experience.
By using our website, you agree to our use of cookies.