The Queensland-New South Wales Interconnector (QNI) upgrade project involves the upgrading of approximately 300km of existing transmission lines to increase the flow of more affordable and reliable electricity between these two Australian states.

The £186m ($230m) project is being jointly undertaken by Queensland’s electricity transmission system operator Powerlink and the New South Wales-based high voltage electricity transmission network operator TransGrid.

The high-voltage alternating current (HVAC) inter-state transmission upgrade project is being developed as part of the Integrated System Plan (ISP) released by Australia Energy Market Operator (AEMO) in July 2018.

The preliminary investigations and project scoping were completed in the second quarter of 2019 while the Project Assessment Conclusions Report (PACR) was submitted after the completion of detailed design and site investigations in the fourth quarter of 2019.

The Australian Energy Regulator (AER) approved the project in April 2020 with the construction works slated to begin in the first half of 2020.

Scheduled for completion in 2022, the QNI upgrade project is expected to generate approximately 150 construction jobs.

The existing QNI transmission system

The existing Queensland-New South Wales Interconnector, which is being operated under a joint operating agreement between TransGrid and Powerlink, is a 330kV high-voltage alternating current (HVAC) bi-directional transmission system with a transfer capacity of 310MW northwards to Queensland and 1,025MW southwards to New South Wales (NSW).

The other existing transmission network between Queensland and NSW includes the Terranora Interconnector, which is a 110kV HVAC double-circuit transmission line between the Mudgeeraba substation in Queensland and the Terranora substation in NSW.

The Queensland-New South Wales Interconnector (QNI) upgrade

The QNI upgrade project is designed to increase the northwards electricity transmission capacity of the interconnector by 460MW from NSW to Queensland and boost the southwards transmission capacity by 190MW from Queensland to NSW.

The project comprises upgrading of 300km of existing transmission lines that involves the replacement of 58 towers between the Liddell power station and TransGrid’s Muswellbrook and Tamworth substations, the replacing, removal and the strengthening of the existing pole structures, the installation of new mid-span structures, as well as the replacement or rearrangement of transmission line insulators.

The project also involves upgrading the substations at Tamworth, Dumaresq, Armidale, and Muswellbrook where conductors and associated equipment will be replaced.

One of the innovative technologies planned to be used for the upgrade project is the installation of static volt amp reactive compensators (SVCs) that will strengthen the system by providing greater voltage stability and regulation.

The upgraded interconnector system will allow NSW to source more affordable and reliable electricity from Queensland to offset the power generation loss due to the scheduled closure of the 2GW Liddell coal-fired power station in 2023.

The project will also lower the cost of renewable electricity provided to the end-consumer in both the sates while enhancing the reliability of the QNI interconnector system.

Project financing

The Australian Federal Government and the NSW Government announced the joint-underwriting of up to £80m ($102m) to support the construction works for the QNI upgrade by TransGrid in October 2019.