A NEW report has shed more light on how the blackout in South Australia occurred and why wind power disconnected from the electricity network.
The Australian Energy Market Operator (AEMO) released its third report today with its preliminary conclusions on the causes of the “Black System” that plunged the entire state into darkness at 4.18pm on September 28.
While tornadoes were found to have taken down three transmission lines ahead of the blackout, the report suggests the system could have continued operating.
Instead it was the loss of power from the state’s wind farms that is thought to be one of the primary causes of the event.
The reduction in wind farm output caused the system to get more electricity from Victoria through the Heywood Interconnector, but the demand was so high that it tripped a safety feature, cutting off supply to the state. This happened within 700 milliseconds.
While some wind farms and other electricity generators remained online and continued to function for a short time, the loss of supply from the interconnector and other wind farms caused the frequency drop to below 47 Hz and they were permitted to disconnect, leading to the blackout.
The AEMO has released 15 recommendations to improve the system and a final report is due to be published in March 2017.
WIND FARM OPERATION
The blackout highlighted that many wind farms have a protection feature which causes turbines to disconnect, stop operating or reduce their output if they experience more than a preset number of voltage dips within a two-minute period.
The AEMO said it was not aware of this protection feature before the SA blackout and this behaviour was not included in any stimulation models the wind farms submitted to AEMO.
Interestingly the AEMO said this type of fault has never been reported to the agency, and it was not aware of any reported instances of this phenomenon occurring internationally.
Wind farms are programmed to recover from voltage dips and some of the wind farms continued to operate and successfully rode through the faults.