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by April Shepherd, Journalist, Utility magazine

The Transgrid Queensland-NSW Interconnector upgrade, which has involved extensive work on substations and transformers, continues to progress, with the project’s goal of boosting interstate transmission capacity and reactive power in the grid close to becoming a reality.

The Queensland-NSW Interconnector (QNI) upgrade aims to ensure a steady power supply for customers by sharing energy across states and the National Energy market (NEM).

The upgrade began in early 2019, with a focus on providing more reactive power support for the grid, and was approved by the Australian Energy Regulator (AER) and fast tracked with support from the NSW and Federal Governments.

The $230 million project is still underway, with an estimated completion date of early 2022 and predictions of a massive $177 million in net benefits to customers once completed.

Transgrid’s QNI Project Director Josh Walker said the project is hoping to achieve more affordable power, support the move towards a renewable future, and enhance energy reliability.

“QNI is largely about providing more reactive power onto the grid, to increase network stability. This has involved major works at three substations to install Static Var Compensators (SVC), associated power transformers, and new capacitor banks,” Mr Walker said.

“QNI is part of our commitment to securing supply in an evolving energy landscape, increasing generation competition and supporting Australia’s transition to a lower carbon future.

“More interstate power flows will boost reliability ahead of the forecast closure of NSW’s Liddell Power Station.

“QNI will increase the power transfer capability between NSW and Queensland by approximately 190MW south and 450MW north.”

The project has passed several major milestones, having moved from the civil construction stage to the electrical installation stage, as well as reaching the 80 per cent completion mark in July 2021.

Substation upgrades at Tamworth, Dumaresq, Armidale, Muswellbrook and Liddell are also speeding ahead, along with installation of SVC transformers.

What does the project involve?

Transgrid is upgrading substations at Tamworth, Dumaresq, Armidale, with minor works at Muswellbrook and Liddell. Major works include the replacement of primary and secondary equipment, the expansion of substation footprints, installation of two SVCs, and installation of nine capacitor banks, to provide greater voltage stability and reactive energy.

The project also includes upgrading 300kms of 50 year old transmission lines, between Liddell Power Station, Muswellbrook and Tamworth substations. This has involved the replacement of 58 tower structures, replacing the old models with a simpler, taller design that allows a greater transfer of power.

Further project works included the raising of transmission line conductors by replacement of insulator arrangements

Key project dates
• Preliminary investigations and project scoping: early 2019
• Detailed design and site investigations: late 2019
• Approval by the AER: April 2020
• Construction starts: May 2020
• Estimated project completion: Early 2022

Substation key works

Dumaresq

Civil works at Dumaresq substation, located in New South Wales close to the Queensland border, are close to completion, with electrical works underway. This substation’s footprint was expanded to make way for the new SVC units, new capacitor banks, SVC transformers and associated switch bays.

SVC units contain technology that can effectively control reactive power on the grid. Specialists from Siemens Energy, who supplied QNI with the technology, will commission the SVC units.

Key civil construction works on the Dumaresq substation include:

• Marshalling boxes
• Lightning mast and light poles
• Busbar supports
• Current breaker supports plus electrical conduits
• Cast in-situ pits, gutters and channels, stormwater and  yard surfacing
• Gantry construction
• Upgrade of towers
• Footprint expanded
• SVC units installed and constructed
• New capacitor banks added
• SVC transformers and associated 330kV switch bays

Crane and elevated platforms were used in capacitor bank energisation at the Armidale substation.

Armidale

Construction of new capacitor banks began in June 2021 at Armidale substation in New England, to enhance power system stability and increase transfer capacity. Four capacitor banks were energised by August 2021.

Key civil construction works on the Armidale substation include:

• Concrete footings, energisation and construction of the 330kV capacitor banks
• Marshalling boxes
• Lightning mast and light poles
• Busbar supports
• Current breaker supports, plus electrical conduits
• Cast in-situ pits, gutters and channels, storm water and yard surfacing
• Gantry construction
• Upgrade of towers

Tamworth

Tamworth substation, situated in north-east New South Wales, is a key aspect in the QNI project, with work beginning on the substation in July 2020. The work at Tamworth is predicted to be completed in early 2022, with capacitor banks likely to be energised in November 2021.

Key civil construction works on the Tamworth substation include:

• Constructing a new SVC compound, to house the SVC switchgear, control systems and three transformers
• Constructing a new services building
• Installing three new capacitor banks and associated switch bays
• Building noise walls and security fencing
• Replacing a transmission tower

Muswellbrook and Liddell

Muswellbrook and Liddell substations are located in the Upper Hunter Region of NSW. Only minor construction works were required at these sites, which include:

• Replacement of equipment substation equipment and conductors

Transmission Lines between Liddell and Tamworth

Works on uprating of the transmission line links were largely completed in July 2021. These works increase the thermal rating of the lines, by raising the conductor heights and clearances. This included:

• Installation of new pole structures
• Removal of old tower structures
• Replacing transmission line insulators/rearranging
• Ground contour re-grading and levelling

The ongoing impact of COVID-19

On interstate projects, collaboration and precise planning is key. Mr Walker said that collaboration and early engagement with design, construction and equipment suppliers was critical to achieving the best outcomes possible for the QNI project.

“Our suppliers have worked with us to drive innovative designs, integrate new technology and equipment into brownfield operational assets,” Mr Walker said.

COVID-19 has brought its own set of challenges to the upgrade, requiring work to be continuously managed by Transgrid in collaboration with State Governments. The pandemic also impacted international supply chains, which was a challenge as equipment was sourced from Europe and Asia.

“There have been issues with staff movements across state borders, as well as out of Sydney and difficulties with the entry of international technical specialists into Australia,” Mr Walker said.

“COVID-19 has also reduced the availability of international shipping. Despite these challenges, all equipment is now on-site”.

Armidale substation during upgrade construction works for the Transgrid QNI project.

The Victoria-New South Wales interconnector

The QNI upgrade isn’t the only interconnector project Transgrid is currently working on; the Victoria-New South Wales Interconnector (VNI) is also underway, aiming to provide shared energy and increased capacity between the two states.

“Both the QNI and VNI upgrades are about improving the supply of lower-cost power to NSW consumers. But the projects are vastly different in scope and execution,” Mr Walker said.

Mr Walker said VNI has been contained to major works at predominantly one substation site, with innovative Smart Wires technology enabling the use of existing transmission lines, whilst QNI required more substation works and SVC installation.

Interconnector boosting industry jobs

A project of this size can provide a significant boost to short-term and long-term employment, from construction jobs, to roles in operations and maintenance.

Mr Walker said the QNI project has seen up to 280 people employed during the civil construction stage of the works. Providing an economic boost to surrounding regions, not just from employment, but for local businesses in accommodation, hospitality and the ancillary sector.

“As well as providing direct employment, there will be longer-term benefits as well, as the new substation equipment will need to be operated and maintained throughout its serviceable lifetime. Maintenance representatives are being familiarised with these new assets through involvement in the commissioning phase, and will be included within their ongoing program of works,” Mr Walker said.

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