Project EnergyConnect, once approved and constructed, will directly link the energy networks of South Australia and New South Wales for the first time.
The largest electricity interconnector project to date in Australia, EnergyConnect is a cornerstone of the Australian Energy Market Operator’s (AEMO) 2020 Integrated System Plan (ISP).
The ISP is a roadmap to ensure Australia has a resilient and secure grid to accommodate future renewable energy, and promote a decarbonised future. The project has passed a cost-benefit analysis, overseen by the Australian Energy Regulator (AER) and is progressing through the final phase of a rigorous approval process.
The challenges of delivering EnergyConnect are being assessed, including the transmission route, the construction of transmission lines and substation requirements.
EnergyConnect will enable the renewable wind and solar energy generated in South Australia to flow into the New South Wales grid, helping stabilise prices in the National Energy Market (NEM).
- Preliminary investigations and project scoping: completed, regulatory approval received in July 2021
- Community and landowner consultation: in progress, from 2018
- Project approvals: in progress, from early 2020 – mid 2022
- Detailed Design and Site Early Works: in progress, early 2021 – mid 2022
- Construction: proposed, from 2022 (NSW Western section)
- Project commissioning: proposed, by 2024
Transgrid will build the New South Wales section of EnergyConnect, ElectraNet will deliver the South Australian component and Secure Energy has been appointed as the primary contractor.
The challenges of distance
Transgrid will construct a 674km transmission line from the South Australian – New South Wales border to Wagga Wagga, linking two existing substations and one new substation.
This isolation, combined with the project’s required 50-year life span, requires that infrastructure choices assure iron-clad network reliability and security.
Yousseph Ters, Transgrid Project Integration Manager, said, “The stability of the network is vital, with outages requiring quick remediation, which will be a challenge given the remoteness of the transmission and substation infrastructure.”
Innovation vs tried and tested technology
Transgrid’s delivery of EnergyConnect includes an estimated 1,900 new transmission towers, linking the three substations to South Australia.
“We need to demonstrate the value that EnergyConnect will provide, balancing the concerns of landholders and affected communities with environmental, heritage and economic constraints,” Mr Ters said.
“Our Network Planning team works closely with team EnergyConnect to choose technical solutions that blend innovative transmission tower technology, with tried and tested substation installations familiar to transmission infrastructure across Australia.”
Transmission towers to suit the terrain
EnergyConnect is using innovative guyed tower technology, consisting of a single mast with guyed wires that spread out diagonally, providing the support required for the tower.
Guyed towers are used extensively in the US, South America, Africa and Europe in locations where the topography is flat. Australia’s grid is often in hilly and rocky areas, so this will be the first use of double circuit guyed towers in Australia, with EnergyConnect using a blend of guyed and self-supporting towers.
“Guyed towers let us clear less space in environmentally sensitive areas. While the permanent footprint is slightly larger, guyed tower construction is significantly less invasive on the landscape and results in an overall better economic outcome for energy consumers,” Mr Ters said.
Helical screw piles aiding water conservation
Transgrid and Secure Energy are investigating the use of helical screw piles for new tower foundations for EnergyConnect – if deemed feasible, the screw piles will save time and money, and be the best environmental choice.
“Helical screw piles are like what they sound. We literally screw the foundations of all transmission towers into the ground with a special machine, rather than dig a foundation and fill it with concrete, which is how towers in Australia are most commonly constructed,” Mr Ters said.
“With this alternative method to build tower foundations, we will save around 6GL of water, the equivalent of 2,400 Olympic swimming pools.”
Helical screw piles also generate a lot less spoil, as foundations do not have to be excavated.
Switchgear solutions future- proofing substations
EnergyConnect will upgrade two Transgrid substations; the Buronga substation, 20km north of Mildura, and the Wagga Wagga 330kV substation.
A new, third substation will be built roughly at the halfway point between the two, 40km south of Coleambally, at Dinawan, which is the local First Nations word for “emu”.
“We needed an intermediary point between the existing substations to add reactive support to the network. Switchgear at Dinawan substation will include reactors, capacitor banks and synchronous condensers,” Mr Ters said.
“The section between Dinawan and Buronga will be 376km, which will be the longest continuous section of transmission line on the Transgrid network. This will also allow for a logical connection point for the proposed South Western Renewable Energy Zone.”
The remoteness of Dinawan and Buronga substations, coupled with EnergyConnect’s regulatory requirements, requires technology resilience at the highest levels.
“We considered a range of different technologies, all of them proven, standard technologies – from gas insulated switchgear, which is highly compact equipment, to air insulated switchgear and a third category called hybrid switchgear, which combines elements of both air insulated and gas insulated,” Mr Ters said.
“We came to the conclusion that air insulated switchgear, which is identical to the majority of what we have on the rest of the network, is best for EnergyConnect”.
Energyconnect’s substation switchgear
The Buronga substation, through EnergyConnect, will become one of Transgrid’s largest substations, converted from 220kV to 330kV. Phase shifting transformers and two of the four synchronous condensers of EnergyConnect will be installed at Buronga.
It will have 15 diameters of breaker and a half 330kV switchgear, which will be the largest on the New South Wales network.
The Wagga Wagga substation switchgear will be upgraded with four new double-switch switch bays, which will improve the reliability of other lines connecting into the substation.
“We have taken a cautious and minimalist approach at the existing Wagga Wagga substation, which was built over 60 years ago,” Mr Ters said.
“For EnergyConnect we have had to consider the most cost-effective completion of the project while considering the needs of future projects currently in the planning phase.”
A new 330kV substation will be built at Dinawan, between Buronga and Wagga Wagga, with the potential to be upgraded to a 500kV site and become an interconnection point for renewable energy supply.
Dinawan substation will provide reactive support with capacitor banks, reactors and two synchronous condensers to manage the voltage on the line, and four breaker and a half diameters of 330kV switch gear.
While being initially operated at 330kV under the EnergyConnect Project, the transmission line from Dinawan through to Wagga Wagga will be able to be operated at 500kV.
Transgrid substation and switchgear equipment used:
5 x 200MVA Phase Shifting Transformer
2 x 100MVA Synchronous Condensers
2 x 52MVA Capacitor Banks
3 x 200MVA 330/220kV Power Transformers
37 x 330kV Circuit Breaker Switchbays
7 x 220kV Circuit Breaker Switchbays
2 x 100MVA Synchronous Condensers
2 x 52MVA Capacitor Banks
10 x 330kV Circuit Breaker Switchbays
Wagga Wagga 330kV (Existing):
8 x 330kV Circuit Breaker Switchbays