Callide Unit C4

Update on Callide C4 recovery and investigation

25 May 2023

CS Energy has completed the bulk of rebuild works on Unit C4 at Callide Power Station and introduced improvements to make the site safer.

CS Energy owns Callide C in a joint venture (JV) with IG Power and operates Callide C on behalf of the JV.

Acting CEO Andrew Varvari said more than 428,000 hours had been worked on the project to repair and rebuild the sections of Unit C4 that were damaged in the incident on 25 May 2021.

“Major replacement components such as the turbine, generator and generator transformer have been installed,” Mr Varvari said.

“A team of 250 employees and contractors worked on this unique and challenging project, and I would like to acknowledge their hard work in reaching this milestone.

Rebuilt Unit C4 May 2023

Image: The Callide Unit C4 turbine hall this month (May 2023).

Video - Earlier this year work crews installed the new C4 generator stator (March 2023).

“The project team is working through a commissioning plan to align with the rebuild of the unit’s cooling tower, as there are some final works that cannot be done until the unit is ready to be commissioned," Mr Varvari said.

“Work has started at site on the project to rebuild the two C station cooling towers, which will involve demolishing both cooling towers and building new structures.

“Independent experts with substantial experience in cooling towers, construction and large project management have been engaged to optimise the cooling tower rebuild program and explore all options to ensure the safe reinstatement of the Callide C units as soon as possible.

“CS Energy continues to engage with the Administrators of IG Power on the cooling tower rebuild works and in relation to longer-term ownership arrangements.”

C4 investigation and safety improvements

Mr Varvari said Dr Sean Brady’s external, independent investigation into the Unit C4 incident was entering its final stages.

“CS Energy has introduced a range of improvements to minimise the risk of an event similar to the C4 incident occurring again and has shared our learnings with industry.

“Our internal analysis of the incident, as well as a report by the Australian Energy Marker Operator, identified that C4’s generator protection systems did not operate on the day of the C4 event, most likely because of a loss of DC power supplies to the unit.

“In response, the JV has modified Callide C’s generator protection system and DC power supplies to improve their reliability and add an additional layer of redundancy.

“We have also reviewed the protection systems on the other units in our portfolio and made improvements to our process safety and operational risk assessment processes.”

Dr Brady said his investigation will make findings from an independent perspective on why the C4 incident happened, including both the technical and organisational factors that could have contributed to the event.

“This is a complex investigation,” Dr Brady said. “The investigation is being conducted by a broad range of subject matter experts, includes independent testing, and involves the collection and analysis of a considerable volume of evidence.”

CS Energy will make further improvements and will share any additional learnings with industry.

Callide Unit C4 is currently forecast to make a staged return to service beginning later this year as follows:

  • 31 Oct 2023 – 300 MW
  • 30 Nov 2023 – 350 MW
  • 31 Jan 2024 – 466MW

Callide Power Station is comprised of two power plants, Callide B and C, each with two generating units (B1 and B2, C3 and C4). CS Energy owns 100 per cent of Callide B and owns Callide C in a 50/50 joint venture with IG Power.