Final AEMO report explains how South Australian blackout happened and makes 19 recommendations

THE final report into last September’s statewide blackout has explained the cascade of events that led to the power meltdown — and made 19 recommendations aimed at preventing another one.

• FINAL REPORT: Better measures needed to avoid another meltdown
• POWER DOSSIER: SA’s energy crisis explained
• 125 days of electricity shortages over next two years
• FIRST REPORT: Multiple faults led to SA blackout
• SECOND REPORT: Why SA wind farms didn’t ride the storms

A LOSS of power from wind farms and tripping of the interconnector to Victoria combined to collapse the stability of SA’s network and deliver the statewide blackout, a new report has found.

The Australian Energy Market Operator has today delivered its final report into the events of September 28, when a major storm triggered a series of events that led to SA’s “system black”.

The report says measures have been taken to ensure wind farms are more able to survive shocks to the system, which resulted from the storm, to reduce the risk of another statewide blackout.

It also finds that the statewide blackout would likely have been avoided if wind farm software settings had been more robust prior to the storm and the automatic shutdowns not occurred.

The report makes a total of 19 recommendations aimed at safeguarding the overall grid.

“The generation mix now includes increased amounts of non-synchronous (wind) and inverter-connected plant,” the report states.

“This generation has different characteristics to conventional plant, and uses active control systems, or complex software, to ride through disturbances.

“With less synchronous generation (coal and gas) online, the system is experiencing more periods with low inertia and low available fault levels, so AEMO is working with industry on ways to use the capability of these new types of power generation to build resilience.”

The report says the cascade of events began with a storm that brought winds up to 260kmh, which brought down major transmission lines in the state’s north and shook the grid.

Nine wind farms out of 13 operating at the time then shut down, pulling 456MW out of the system in seven seconds and resulting in a surge in draw over the Victorian interconnector.

The interconnector than failed due to huge extra demand, leaving SA to fend for itself.

At that point, frequency in the SA power island collapsed and sent the state black.

“Approximately 700 milliseconds after the reduction of output from the last of the wind farms, the flow on the Victoria — SA Heywood Interconnector reached such a level that it activated a special protection scheme that tripped the interconnector offline,” the report finds.

“The SA power system then became separated, “islanded”, from the rest of the NEM.

“The remaining generation was much less than the connected load and unable to maintain the islanded system frequency. As a result, all supply to the SA region was lost at 4.18pm (EST).”

The report says settings on wind farms have been changed to help them through shocks. It indicates having those settings in place before the storm may have stopped a statewide blackout.

“Changes made to turbine control settings shortly after the event has removed the risk of recurrence given the same number of disturbances,” the report says.

“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.

“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.”

It says other measures are also needed to protect SA from another statewide blackout that include more technology which can ride through shocks and maintain stable frequency.

Federal Energy Minister Josh Frydenberg has labelled the findings of today’s report a “wake-up call” and that issues surrounding wind farms were at the root of the blackout.

“The statewide blackout in South Australia was a wake-up call that underlines the importance of maintaining the supply of reliable electricity to all Australians,” he said.

“AEMO’s final report confirms that the sequence of events of the blackout remains unchanged, starting with a storm damaging the transmission network.”

“The report makes clear that the statewide blackout would not have occurred if the wind farms had ridden through a number of voltage disturbances across the network.”

“Importantly it was the “settings” within the majority of the wind farms which meant they could not ride through the voltage disturbance caused by the storm.”

“Notwithstanding action has now been taken to address these wind farm settings, AEMO’s conclusions from its final report will be an important input into the Finkel Review.”