The operator of South Australia’s high-voltage electricity transmission infrastructure was warned of the risk of tower collapse a decade ago because of poor maintenance, sparking calls for more investment in Australia’s power network in the wake of South Australia’s statewide blackout.
The transmission company ElectraNet in South Australia owns and operates some of the oldest electricity transmission network assets in the nation, with half of the state’s electricity towers due to exceed their use-by dates by 2023.
On Wednesday, supercell storms with cyclonic winds ripped 22 transmission towers in South Australia’s mid-north out of the ground, bringing down three major transmission lines, which is believed to have caused the frequency of the grid to drop to a point where an automatic shutdown of the entire system was triggered. Temporary, replacement transmission towers are expected to arrive in the next few days from interstate.
ElectraNet was first warned in 2005 of the risk that 43 of its towers could collapse in windy conditions because of corrosion and degradation of foundations.
Nearly a decade later, ElectraNet sought approval from the Australian Energy Regulator to recoup the cost of repairing the towers in its asset refurbishment plan for 2013 to 2018. The company noted that in some cases, foundation reinforcement bars and stubs were missing.
ElectraNet executive manager Rainer Korte yesterday said severe weather that had battered South Australia since Wednesday afternoon meant “forces were put on sections of the lines that they were unable to withstand”.
Mr Korte insisted none of the towers brought down on Wednesday had been identified as needing repair and could not say how old those towers were.
ElectraNet had wanted to spend $750.1 million over five years from 2013 to build new facilities or replace ageing transmission infrastructure but the regulator said $691m was sufficient. Company documents show more than 70 per cent of ElectraNet’s capital investment program is focused on replacing and refurbishing the state’s ageing infrastructure.
More than 80 per cent of transmission line failures in Australia are due to high-intensity winds. Energy experts yesterday warned that the ageing infrastructure would be unlikely to meet today’s minimum standards for overhead lines to withstand strong winds.
Energy Networks Association chief executive John Bradley said Australia’s energy infrastructure would be a major driver of network costs for at least the next decade.
With much of Australia’s electricity network built in the 1970s with a working life of up to 40 years, there was a significant need to invest in new infrastructure, he said: “The South Australian event just underscores the need for timely investment in secure and reliable network infrastructure.”
ElectraNet said its towers were “fit for purpose” as they had worked satisfactorily for the past 50 years.
Queensland University engineer Matthew Mason said damage to towers from winds “generally happens on older line systems”.
“In the last few decades, regulations have been introduced regarding wind speeds they need to be designed for,” Dr Mason said.
“The older stock is not designed to that same standard and generally performs more poorly.”
The South Australian government confirmed that during the storm, a lightning strike hit AGL’s Torrens Island Power Station, the state’s primary gas-fuelled baseload generator. While this could have triggered the shutdown of the state’s main conventional power generator, AGL spokesman Craig Middleton said the plant’s systems did not indicate the lightning strike caused the plant to trip.