The AER alleges AGL Energy Ltd, Neoen SA, Pacific Hydro Ltd and Tilt Renewables breached the National Electricity Rules after “severe weather conditions led to significant damage to South Australian transmission lines causing voltage disturbances”.

“A subsequent loss of wind generation contributed to a State-wide black-out or black system event,” it said.

“The AER alleges that each of these wind farm operators failed to ensure that their plant and associated facilities at the relevant wind farms complied with their generator performance standard requirement to ride-through certain disturbances.

“In addition, the AER 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.”

The storm on September 29, 2016, produced two tornadoes with wind speeds between 190 and 260 kilometres per hour which toppled towers and felled three 275kv transmission lines.

About 850,000 customers lost power during the late afternoon blackout which plunged most of the state into darkness, with some in the state’s north and on the Eyre Peninsula left without power and services including mains water for days.

An AER investigation in 2018 said while most of SA’s power supply was restored within eight hours, “the wholesale market in SA was suspended for 13 days”

Photo: AAP/David Mariuz

It described the 2016 blackout as a “serious state-wide event, ultimately brought about by extreme weather, and in many cases unprecedented circumstances, impacting energy infrastructure in South Australia”.

AER court action against AGL relates to its Hallett 1, Hallett 2 Hallett 4 and Hallett 5 wind farms, as well as Neoen’s Hornsdale wind farm, Pacific Hydro’s Clements Gap wind farm and Tilt Renewables’ Snowtown 2 wind farm.

“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” chair Paula Conboy said.

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

AER is seeking declarations, penalties, compliance program orders and costs.

In March 2017, the Australian Energy Market Operator (AEMO) released its final report into the 2016 blackout, finding that too-sensitive settings in some wind farms triggered the “black system” event, and not the intermittent nature of wind energy generation.

“Had the generation deficit not occurred, AEMO’s modelling indicates SA would have remained connected to Victoria and the black system would have been avoided,” the report said.

“AEMO cannot rule out the possibility that later events could have caused a black system, but is not aware of any system damage that would have done this.”

Inquiries found that the storm’s damage to three transmission lines caused them to trip, with a sequence of quick faults resulting in six voltage dips on the SA grid over two minutes.

As network faults grew, the power output of some SA wind farms dropped quickly as their protection settings activated.

Victoria’s Heywood Interconnector pumped more power into the system, but flow hit a level that triggered a protection system which tripped it offline and sent frequency into the SA grid plummeting.

While the state has an automatic load-shedding system, frequency change happened so quickly that it failed and the system collapsed, separating the SA power system from the national grid.

AEMO said analysis showed that “following system separation, frequency collapse and the consequent black system was inevitable”.

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