An explosion in the plant's turbine hall resulted in a trip of multiple generators and high-voltage transmission lines across Queensland, leaving 470,000 homes and businesses without power.

The regulator alleges Callide's C4 unit failed to ensure its plant met performance standards and did not design its facilities to comply with those requirements.

"The failure of Callide C4’s protection systems to disconnect the generating unit from the power system resulted in the trip of multiple generators," the regulator said in a statement. 

Regulator board member Justin Oliver said compliance with generator performance standards is critical.

"It’s vital that registered participants and generators are aware of their performance standards and comply with them at all times so that the market and consumers aren’t wrongly exposed to the consequences of adverse events," Mr Oliver said. 

The Callide C plant can generate up to 1540MW of electricity - about 30 per cent of the state's overnight demand.

Callide B's two units, which are run by state-owned electricity generator CS Energy, were quickly back in operation following the incident.

The repair of units C3 and C4 has been delayed through 2023 and now into 2024, with their partial return to service expected on February 29 and June 30 respectively. 

A spokesperson for CPT said they will work co-operatively with the regulator to resolve the matter as soon as possible.

The regulator is seeking pecuniary penalties, declarations, orders for remedying the breach or preventing the recurrence of the breach, and costs.

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