Callide C failure review leaves questions still to be answered
The failure of battery backup systems has been blamed for Queensland’s Callide coal plant explosion which slashed power from the east coast grid and triggered mass blackouts.
The operator of the Callide C plant could not have predicted the series of cascading failures that caused the explosion of the plant in 2021, according to CS Energy boss Darren Busine.
The state-owned power company released a summary of an internal technical report on the explosion on Tuesday, outlining the series of failures of the plant’s backup systems and describing the catastrophic failure as the “simultaneous failure of key
electrical equipment and system back-ups in a series of complex events that could not have been anticipated”.
The summary was released only days after the Australian Energy Regulator launched legal action against the trading arm of the energy plant, but Mr Busine denied there was any link between the release of its internal review and the AER’s action.
“This is not a defence to the energy regulator. The energy regulator needs to do their actions. What is clear is that the system was impacted on the day - that’s what the Australian energy regulator has taken action against the Callide power trading joint venture entity over,” Mr Busine told reporters on Tuesday.
The explosion of the C4 turbine at Callide C forced the evacuation of the plant, and immediately stripped about 10 per cent of Queensland’s generating capacity out of the east coast grid. Callide C suffered a second mysterious catastrophe in October 2022, when part of the cooling towers collapsed.
The documents made public on Tuesday are unlikely to satisfy critics of the Queensland government and CS Energy, as they only explain the events that occurred immediately ahead of the explosion and catastrophic failure, and make no reference to any underlying factors that may have contributed to the incident.
An independent expert report by forensic engineer Sean Brady is still to be delivered, more than 30 months after it was commissioned in June 2021, but CS Energy said its own report was compiled with the help of “a range of experts including Aurecon and independent investigator Dr Sean Brady”.
Liberal National Party energy spokeswoman Deb Frecklington said the CS Energy report, accompanied by a “sanitised video”, provided no real answers about what caused the explosion.
“It’s been 994 days since the catastrophic explosion at Callide that set power prices through the roof and what has this government done? Absolutely nothing,” she said.
“Power plants don’t explode if maintained properly, but under Labor that’s exactly what happened at Callide.”
The union that covers workers at the plant, as well as the private investors in Callide C, have both previously expressed concerns that poor maintenance by CS Energy – which operates and owns half of the plant – was ultimately to blame for its failure.
The report blames the failure of battery backup systems for the explosion, saying that maintenance upgrades for the battery at Callide’s C4 unit meant the plant’s safety systems did not detect a failure inside the unit and power down the generator’s turbine in time to prevent it overheating and igniting hydrogen gas usually used to cool down the generator.
The immediate cause of the explosion, according to documents released by CS Energy on Tuesday, was the failure of turbine lubrication systems, followed by the failure of generator protection systems after the generator initially tripped because battery backups also failed, leaving the turbine “motoring” – spinning, but providing no power.
“These protection systems did not detect the motoring and de-energise the generator in a timely manner to prevent damage,” the report says.
CS Energy said the design of the plant was partly to blame for the failure, as it limited the reliability of the battery backups for emergency systems. Cascading failures of other systems ultimately led to the circumstances of the explosion.
A 2021 report into the incident by the Australian Energy Market noted that maintenance to backup power supplies appeared to be a contributing factor in the disaster, as it meant sensors and protection equipment at the plant were not operating.
CS Energy’s report mirrors that of AEMO, noting that automatic safety equipment were offline at the time, after being damaged during a January 2021 incident at Callide, but that the modifications made to the plant were not yet complete.
Ms Frecklington lashed Energy Minister Mick de Brenni and Treasurer Cameron Dick - who are shareholding ministers in CS Energy - for failing to provide answers about the explosion after almost three years.
“Why do they deserve to serve the paycheck of a shareholding minister if they have no clue what’s going on?” she said.
“I bet they’ve got that (Brady) report, I bet they’ve been sitting on it.”
Mr de Brenni said Ms Frecklington’s allegations were “serious” and incorrect.
“I place on record the government has not received the Brady report and we have been advised that it is not yet finalised,” he told parliament.
“I want to stress that the technical report released today is just the first piece of information that will be available.
“The government will let Dr Brady, one of the nation’s preeminent engineers, do his job and when his report is finished, we will consider how we will respond.”
