From the AEMO:
The Australian Energy Market Operator (AEMO) has today published a preliminary operating incident report into the South Australian state-wide power outage (referred to as ‘SA region Black System’) that occurred at 16:18hrs Australian Eastern Standard Time (AEST) on Wednesday, 28 September 2016, during severe storm activity in the state.
AEMO has prepared this preliminary report as part of its review of power system events, under the National Electricity Rules (Rules). The observations noted in this initial report are based on early data and information up to 9.00 am, Monday, 3 October 2016.
The preliminary report explains how severe weather moved through South Australia on the afternoon of Wednesday 28 September 2016, with high winds, thunderstorms, lightning strikes, hail, and heavy rainfall. The weather resulted in multiple transmission system faults including, in the space of 12 seconds, the loss of three major 275 kV transmission lines north of Adelaide.
Generation initially rode through the faults, but at 16:18hrs, following multiple faults in a short period, 315 MW of wind generation disconnected, affecting the region north of Adelaide. The uncontrolled reduction in generation increased the flow on the main Victorian interconnector (Heywood) to make up the deficit and resulted in the interconnector overloading.
To avoid damage to the interconnector, the automatic-protection mechanism activated, tripping the interconnector and resulting in the remaining customer load and electricity generation in SA being lost. This automatic-protection operated in less than half a second at 16:18hrs and the event resulted in the SA regional electricity market being suspended.
While the event was triggered by extreme weather, AEMO will conduct a thorough investigation into how each component of the electricity system responded under these circumstances. In an ever-changing environment, AEMO’s ongoing responsibility continues to be to safely and securely manage the power system and wholesale electricity markets to deliver energy security for all Australians.
AEMO will continue to analyse the events of last Wednesday and will provide a further update on Wednesday 19 October. AEMO expects that a detailed report on the SA region Black System, including recommendations, may take up to six months to complete.
And the sequence:
It appears there were both wind farm and transmission failures: