South Australia's renewable power mix was a factor in the state's rare September blackout during wild storms, a new report says.
The Australian Energy Market Operator on Monday released its third preliminary report into the September 28 "black system" event.
Previous reports said a series of tornadoes caused a sequence of faults that plunged the state into darkness and left it isolated from the national power grid.
Monday's report discusses SA's energy mix.
It found that immediately prior to the blackout, 883 megawatts of the state's electricity was being provided by wind farms, compared to 330 megawatts of gas and 613 megawatts of electricity imports via Victoria.
The security of the power grid supply relies on voltage control and frequency control, or all the interconnected generating machines on the grid spinning in lock step.
There is now more non-synchronous power, like wind, flowing into the grid, which requires changes to the way the power system is managed.
In Melbourne on Monday, AEMO chair Tony Marxsen said tornadoes and a severe storm caused the blackout - which brought down three major transmission lines within 87 seconds.
He said a number of wind turbine generators in the mid-north exhibited a reduction in power or disconnected as the number of faults grew - but it was unclear whether the weather or reduced power caused the widespread blackout.
"While we may conclude in time, that the blackout was due solely to the 500 megawatt reduction, we will probably never be able to state with complete confidence that a later circumstance in the ongoing storms would not have produced a similar result," Dr Marxsen said.
He spoke briefly about the 15 recommendations outlined in the preliminary report, saying AEMO would work with stakeholders to reduce the risk of islanding the SA network from the national grid and address technical issues highlighted by the September 28 event.
The fourth and final report will be published in March 2017.
AEMO recommendations include:
* More rigorous monitoring of weather warnings to trigger reassessment of reclassification decisions when relevant.
* Develop a more structured process for information exchange and reclassification decisions when there are extreme wind speeds, including tornadoes.
* Investigate developing a system protection scheme that would initiate, if necessary, load shedding or generation shedding.
* Investigate the level of risk to power system security posed by a single credible fault in areas where there is a concentration of wind farms.
