The Australian Energy Regulator is taking a coal-fired Queensland power station to court over an explosion that left nearly half a million homes without power. 

In May 2021, multiple generators and high voltage transmission lines in Queensland were tripped following an explosion in the C4 unit at the Callide Power Station in Biloela, central Queensland. 

The incident caused nearly 500,000 customers to lose power, from the NSW border to north of Cairns.

On Friday, the Australian Energy Regulator (AER) began legal proceedings in the Federal Court, alleging Callide Power Trading broke National Electricity Rules, failing to comply with its own performance standards for Callide C4. 

The AER alleges the C4 unit did not have sufficient energy supply to disconnect the generating unit when the faults occurred on the day of the explosion, nor did it have a protection system to promptly disconnect it.

AER board member Justin Oliver said adhering to generator performance standards was “critical” to safe operations. 

“Failure to comply with these standards can risk power system security, see consumers disconnected from power supply and cause wholesale energy prices to increase during and beyond these events,” Mr Oliver said.

When will it come back online?

Following the C4 explosion, in 2022 generator C3 was also taken offline in an incident involving structural failure. 

Efforts to bring both units back online have been plagued with delays. 

CS Energy said last month the C3 unit would return to service by the end of March, while the C4 unit was expected to be back online fully by the end of July.

Callide Power Trading, which is the market participant for Callide C Power Trading, is owned in a joint venture.

IG Power owns 50 per cent, while the other half is owned by Callide Energy, a subsidiary of the Queensland government company CS Energy.

In a statement on Friday, Callide Power Trading said it would work co-operatively with the AER to resolve the matter “as soon as possible”.

Voluntary administrators were appointed to IG Power in March last year.

In a separate matter, last month the Federal Court ordered IG Power to appoint special administrators with powers to complete a new investigation into the incidents at the power station.

There is no set date for when the AER’s matter will be heard before the Federal Court.