Comparing High Voltage Overhead and Underground Transmission Infrastructure (up to 500kV)

27 November 2023

Original story posted here.

A new report by Curtin University and The University of Queensland has provided insights into the trade-offs between overhead and underground transmission lines and the challenges of expanding Australia’s grid for renewable energy initiatives.

The federal government has set a goal of more than 80 per cent of electricity coming from renewable energy by 2030, and one of the key pillars of this transition is the expansion of the grid to connect regional wind and solar projects, which involves new or upgraded transmission lines.

The ‘Comparing High Voltage Overhead and Underground Transmission Infrastructure’ report delves into the complexities of this endeavour, recognising the technical, economic, environmental and social constraints that impact society’s response.

Report lead author and Director of the Curtin Institute for Energy Transition Professor Peta Ashworth said the research underscores the need for increased public understanding of why new transmission infrastructure is needed and the trade-offs involved.

“While the decarbonisation of Australia’s energy system is a global imperative, an informed and engaged public is crucial to ensuring fairness and understanding during this transformative journey,” Professor Ashworth said.

“Our research makes it clear that without strategic grid expansion, a successful transition to an eco-friendly economy is at risk and navigating the challenges ahead requires strong leadership, community involvement and fair consideration of all stakeholders.”

Co-author Professor Tapan Saha from The University of Queensland’s School of Electrical Engineering and Computer Science said the report also found from a technical standpoint, high voltage alternating current (HVAC) underground cable transmission, while feasible, is limited to relatively short lengths due to the high electrical capacitance of transmission cables. High voltage direct current (HVDC) transmission can be considered as a viable option for long point to point connections and other specific applications.

“The challenges of underground cable transmission are rooted in the significant charging currents associated with their highly capacitive characteristics and reactive power compensation plants are necessary to mitigate the resultant energy losses, making this option economically demanding,” Professor Saha said.

This research was funded by Powerlink, a government owned corporation that develops, operates and maintains the high voltage electricity transmission network in Queensland.


Download Summary Report   Download Comparison Table

Research Background

Based on the experience of transmission network service providers (TNSP) in other states Powerlink Queensland commissioned this collaborative research project between Curtin University and The University of Queensland.  The aim of which was to provide the latest independent scientific information to inform a clear and consistent approach to the consideration of undergrounding of transmission infrastructure and the associated trade-offs.

While transmission line projects are very technical in nature, it is impossible to ignore their impacts on the local environment, individual stakeholders and the wider communities they are being proposed for.  The importance of which was highlighted by the Australian Energy Infrastructure Commissioner (AEIC) in his submission to the Australian Energy Market Commission – Transmission Planning and Investment Review (16th August, 2022). The Commissioner highlighted:

The timely approval and efficient delivery of large-scale transmission projects that enable the significant energy transition in Australia to occur, whilst ensuring that potential impacts of such projects to regional communities and landholders are appropriately managed, is likely to be our collective highest priority for this decade.

Recognising that no two situations will be the same, this research combines the latest technical knowledge with a review of environmental, social and economic considerations. It systematic approach provides a credible baseline from which to engage key stakeholder groups for input into the trade-offs associated with the choices surrounding transmission line infrastructure deployment.