Two South Australian wind farms have argued they should not shoulder the blame for the 2016 statewide blackout, a court has heard.
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The Australian Energy Regulator is taking legal action against four energy companies over the incident.
But the Federal Court heard on Tuesday two of the wind farms - at Clements Gap and Hornsdale - are arguing they are not liable because the state's power system was not in a secure operating state at the time of the blackout.
Tom Clarke, for the AER, told the court "secure operating state" is a technical term with a specific definition relating to power supply.
He said the two companies involved say that performance standards in relation to a blackout only apply if the system is operating securely.
"The respondents, Pacific Hydro and HWF contend... that the power system was not in a secure operating state at the time," he said.
"The AER does not agree with that."
Mr Clarke said the case could go to trial towards the end of next year.
The 2016 outage was triggered by a severe weather event that swept across the state, damaging more than 20 towers in the Mid North and bringing down major transmission lines.
About 850,000 customers lost power, with some in the north and on the Eyre Peninsula left without electricity for several days.
An Australian Energy Market Operator report, released about a month later, found nine of 13 wind farms online at the time of the blackout switched off when the transmission lines came down.
It found the inability of the wind farms to ride through those disturbances was the result of safety settings that forced them to disconnect or reduce output.
In its action, the AER alleges each of the wind farm operators failed to ensure their plant and associated facilities complied with their standard requirement to ride-through certain disturbances.
It also alleges the wind farm operators failed to provide automatic protection systems to ensure continuity of supply in contravention of the National Electricity Rules.
The AER is seeking declarations, penalties, compliance program orders and costs from AGL Energy Ltd, Neoen SA, Pacific Hydro Ltd and Tilt Renewables.
The court has previously heard scientific evidence will play a role in establishing responsibility before any question of penalty can be examined.
The regulator has also launched legal action against the owners of the Pelican Point Power Station after it failed to notify authorities it had spare generator capacity during blackouts in February 2017.
Australian Associated Press
