Turbine technology |
Callide C4 incident: counting the costs
Callide Power Trading has been ordered by the Federal Court to pay a penalty of $9 million for breaches of the Australian National Electricity Rules (NER), which resulted in catastrophic failure of the steam turbine generator of Callide C unit 4
In proceedings brought by the Australian Energy Regulator (AER), Callide Power Trading admitted that on 25 May 2021 it failed to ensure the Callide C4 coal-fired generating unit met or exceeded its performance standards as required under the NER. It also admitted that it failed to plan and design its facilities and ensure they were operated to comply with its performance standards, also in breach of the NER. With a maximum penalty of $10 million, the $9 million penalty is the highest ever imposed for a failure to comply with performance standards under the NER.
The catastrophic failure and destruction of Callide C4 had widespread impacts. The disconnection caused major disruption to energy supply and required AEMO to activate emergency reliability measures.
The plant damage resulted in Callide C4 being out of service for nearly two years. It remained offline until 30 August 2024 due to unrelated incidents.
AER Chair Clare Savage said the Court’s decision reflected the seriousness of the breach by Callide Power Trading.
“In the immediate aftermath of the event, the energy supply for almost half a million customers was disrupted and the spot price for electricity in Queensland and New South Wales significantly increased.
“This significant penalty reinforces the importance of generators and Registered Participants [ie, participants in the Australian energy market] who are responsible for generators, complying with performance standards to ensure the security and safety of the power system.
“Those responsible for generators must have appropriate systems, processes and protocols
in place to ensure they and their operators can comply with their regulatory obligations.” Justice Derrington said: “… the penalty of $9 000 000…should be understood by others in the industry as reflecting the seriousness with which the Court regards the two contraventions admitted by Callide Power Trading.” In addition to ordering Callide Power Trading to pay the penalty, the court ordered it to pay $150 000 towards the AER’s legal costs. The Callide C4 event occurred on the afternoon of 25 May 2021, during a planned procedure to replace the battery charger for the Callide C4 generating unit.
The event caused the catastrophic failure and destruction of the Callide C4 generating unit (commissioned in 2001), and was followed by significant, long-term and wide-ranging impacts on the National Energy Market and on energy consumers in Queensland and northern New South Wales.
There were no injuries or fatalities but some 3045 MW of generation was lost, and 2300 MW of customer load was disconnected from the power system resulting in widespread blackouts to households and businesses across Queensland.
After conducting a thorough investigation, on 9 February 2024 the AER instituted proceedings in the Federal Court against Callide Power Trading Pty Ltd for failing to comply with its performance standards for the Callide C power station. The penalty decision was handed down on 4 February 2025.
Root causes – the Brady Haywood report
A report by engineering consultancy Brady Haywood, Technical and organisational
investigation of the Callide unit C4 incident, published in July 2024, investigated the root causes of the catastrophic event. Some of its key findings are summarised below. The report notes that the Callide 4 steam turbine rotor shaft was held in position by bearings situated at eight locations along its length, as illustrated in the diagram on page 25. The bearings consist of cylindrical sleeves that are pumped with pressurised oil to provide a thin film of lubrication oil between the rotor shaft and bearings. This allows the rotor to spin freely without metal-on-metal contact. Inside the generator, the rotor is cooled by pressurised hydrogen gas. To prevent hydrogen escaping, a seal is created by pumping pressurised oil into the small gap between the rotor shaft and generator casing at each end of the generator.
Unit C4 relies on two electrical systems: an AC system and a DC system. These provide electrical supply to the unit.
The AC system supplies most of the equipment required for the unit to operate. This includes equipment that provides lubrication oil to the bearings, equipment that provides cooling for the unit, and equipment that opens and closes valves.
The DC system supplies the unit’s protection, control, and monitoring systems. It also supplies back-up equipment, such as the emergency lubrication oil pumps. The protection, control, and monitoring systems detect and respond to faults in the unit. For example, if AC supply is lost, they can disconnect the unit from the grid and shut it down safely.
The unit C4 DC system is supplied by a battery charger and a battery. The battery charger is the primary source of supply to the DC system, with
Callide unit C4 steam turbine after the incident (source: CS Energy) 22 | March 2025|
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