Richard got it right!
Would all you non-technical people (plus the climate change change deniers, AND the green enegy zealots) please stop talking uninformed rubbish and go away. The electricity supply network is very large, and system stability is a black art. I know an old engineer from the ElCom days who told me that in the 80s if three or four transmission lines runnning next to one another near Sydney were taken out by some disaster (e.g. plane crash - but irrelevant) then it was likely that the NSW network would have gone unstable, and that's with NO loss of (nearly 100% coal) generation or load. That's because all the generators have to remain in synchronism - and that's tricky when components are hundreds of kilometres apart. Even though electricity travels at the speed of light the delays from one end of NSW to the other are very significant compared to a couple of degrees phase difference at 50 Hz. So the rapid sequence of faults and loss of transmission lines in the SA case meant a network outage was a near certainty.
Some unconfirmed information I have indicates that Richard's guess about the reason for some wind generation dropping off near the end of the "event" was spot on - the wind farm protection systems apparently operated as designed, because they detected a sequence of frequency and voltage swings.
Instead of wasting time arguing about wind power versus gas/coal/nuclear/blah blah the big question we should be asking is why so many transmission towers (22 or 23?) blew over. Very rarely happens in other states - even Queensland which regularly gets cyclones. Is SA skimping on maintenance? The pollies won't go there because it might raise embarrassing questions about privatisation and government oversight.