Transgrid says it has unveiled one of the biggest and most sophisticated substations in the Southern Hemisphere, with the completion of the Buronga substation.

The completion occurred as powerlines from the new powerline from Buronga to Wagga Wagga were strung across the Cobb Highway between Hay and Deniliquin last month.

The exercise involved several mammoth cranes to lift and attach cables, and multiple workers on site to control traffic.

Timber power poles and harnesses were suspended in the air, designed to catch the cables if they fell, protecting the traffic crossing the Hay Plains.

The Buronga substation is 15 hectares in size comprising 24,000m3 of concrete and sophisticated electrical equipment from around the world, including synchronous condensers, phase shifting transformers, shunt reactors, step down transformers, power transformers and capacitor banks.

According to Gordon Taylor, Transgrid's Executive General Manager of Major Projects, the new substation is a critical part of the EnergyConnect interconnector project, which will improve the reliability and security of the National Electricity Market as older coal-fired power stations are retired.

"The 900km interconnector will give households and businesses in NSW, South Australia and Victoria access to clean, affordable renewable energy, putting downward pressure on energy bills and helping Australia meet its net-zero targets," Mr Taylor said.

"We are proud to have delivered this sophisticated and world-class substation at Buronga, which will direct and balance power flows between three Australian states," Elecnor Australia's EnergyConnect Project Director Felipe Delgado.

"The scale and engineering complexity of this substation is unlike anything else in Australia.

"Working alongside our delivery partners across civil, structural, mechanical and electrical disciplines, we overcame engineering challenges, to integrate highly specialised equipment from around the world."

The project reached its final milestone with the energisation of the last section of the substation, which will increase capacity from 150 megawatts to 800 megawatts.

This will happen after the eastern section of the project—the 540 kilometre line between Buronga and Wagga Wagga—is completed.