AEMO considered an underground option in the early stages of the Western Victoria RIT-T. Market and industry information indicated that per kilometre, building transmission cables underground would be in the order of up to 10 times more expensive compared to the equivalent overhead option. In comparison, an overhead option would deliver similar network benefits at a significantly lower cost to Victorian electricity consumers, who will ultimately fund this project.
High Voltage Direct Current (HVDC) can be used overhead or underground. It was excluded as a credible option due to the need for multiple (minimum of four), expensive, large ‘converter stations’ to be built to integrate a HVDC solution into the existing network, which is High Voltage Alternating Current (HVAC). If HVDC were to be used, all future generators would require an above-ground converter station, too. This is due to the need for associated infrastructure to integrate a HVDC solution into the existing network which is High Voltage Alternating Current (HVAC). Additional infrastructure may also be required to maintain adequate system strength.
Given the reduced flexibility for future generation connections, the cost of converter station infrastructure, and the additional system strength requirements, in this instance HVDC could not be considered technically or economically feasible under the RIT-T application guidelines. Accordingly, it was not included in market modelling as a credible option.
AEMO is not currently aware of any new information that contradicts the conclusion that an underground installation of the WVTNP would be significantly more costly. However, we acknowledge the public interest in seeing further details comparing underground designs relative to the proposed overhead project. Following the Environment Effects Statement (EES) scoping requirements provided by Victoria’s Department of Environment, Land, Water and Planning (DELWP), AusNet Services will consider undergrounding as well as a range of other project alternatives through the EES process.