The Australian Energy Regulator (AER) has launched legal proceedings against wind farm operators over South Australia's 2016 blackout.

The AER is taking action in the Federal Court against subsidiaries of AGL, Neoen, Pacific Hydro and Tilt Renewables.

The regulator alleges the companies did not comply with performance requirements to ride through major disruptions and disturbances, and also breached the National Electricity Rules.

“The AER has brought these proceedings to send a strong signal to all energy businesses about the importance of compliance with performance standards to promote system security and reliability,” AER chair Paula Conboy said in a statement.

“These alleged failures contributed to the black system event, and meant that AEMO [Australian Energy Market Operator] was not fully informed when responding to system-wide failures in South Australia in September 2016.”

The blackout occurred on September 28, 2016, when extreme weather damaged electricity infrastructure, knocking down transmission lines.

The AER claims a subsequent loss of wind generation then triggered a blackout, leaving 850,000 people without power.

It alleges that the wind farm operators failed to provide automatic protection systems to enable them to ride-through voltage disturbances to ensure continuity of supply, in contravention of the National Electricity Rules.

It is seeking to impose penalties against the four companies.

“Providing timely and accurate information to AEMO is critical in ensuring power-system security and the effective operation of the wholesale energy markets,” Ms Conboy said.

AGL says the allegations against it are “highly technical in nature”, but it “considers that it has complied with its legal obligations in relation to the [blackout]”.

The company said it did “not accept the AER's conclusions” and would “strongly defend these proceedings”.

“We are committed to working with the regulator and stakeholders to ensure the integrity of the energy market and the ongoing stability of South Australia's electricity system,” it stated.

AGL insists it complies with national energy rules, and blamed the situation on a “catastrophic storm”.

“Weather experts described the event as a once-in-50-year storm, with 80,000 lightning strikes and tornadoes with wind speeds reaching up to 260 kilometres an hour.”

Tilt says it “acted in good faith and in accordance with the applicable National Electricity Rules”, and has pledged to “continue to engage with the AER in an endeavour to resolve this matter”.

The Australian Energy Regulator (AER) has launched legal proceedings against wind farm operators over South Australia's 2016 blackout.