Callide Unit C4 recovery
This page contains information about the process safety incident that occurred on Callide Unit C4 incident in 2021, investigations into its cause, and the return to service of the unit.
key milestones
BACKGROUND
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 (JV) with IG Power.
On 25 May 2021 an incident occurred on Unit C4, which resulted in an explosion and substantial damage to the unit, forcing it offline. Shortly afterwards Callide’s other operating units tripped and went offline. Multiple power stations and high voltage transmission lines in Central Queensland also tripped, leading to a significant reduction of load and temporary separation between Queensland and the rest of the NEM.
Our first priority was to make sure workers and the Callide site were safe. The power station was fully evacuated and nobody was injured.
CS ENERGY TECHNICAL INVESTIGATION
CS Energy is committed to understanding the facts that led to the incident so we can learn from it and improve the safety of our people and plant.
On 13 February 2024 we released a report on the technical contributing factors to the Callide Unit C4 incident and the actions we have taken to prevent a similar event from happening again.
Download our report: Callide Unit C4 turbine generator failure - Technical investigation summary (PDF 1.3MB)
We have introduced a range of safety improvements and have shared our initial learnings with other power station operators.
Our internal analysis, as well as a report by the Australian Energy Marker Operator, identified that Unit 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.
We have carried out work to enhance Callide C’s generator protection systems and DC power supplies, and improvements have been made to DC supplies at Kogan Creek Power Station, following a review of its DC supplies and protection systems.
We have also updated electrical access procedures, and our operational risk assessment processes that apply to all of our sites.
CS Energy will make further improvements and will share any additional learnings with industry.
INDEPENDENT INVESTIGATION
Dr Sean Brady from Brady Heywood led an external, independent investigation and review of the incident.
CS Energy released the Brady Heywood report into the Unit C4 incident on 17 July 2024, alongside CS Energy's response plan for building a safer, better business.
Brady Heywood - Technical and Organisational Investigation of the Callide Unit C4 incident (PDF 27.9MB)
A safer, better CS Energy (PDF 527.3KB)
UNIT C4 RECOVERY
CS Energy returned Unit C4 to service on 30 August 2024.
Returning Unit C4 to service has been a unique and complex project. A team of employees and contractors worked more than 570,000 hours on the Unit C4 recovery. This included replacing major components that were damaged in the C4 incident including the turbine, generator and generator transformer.
The return to service of Unit C4 also included the rebuild of its cooling tower as part of a separate project - the Callide C cooling towers rebuild project.
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