Bazz,

It wasn't just the wind turbines that the increasing load caused to disconnect - it was the gas turbines too.

Does "choppers" have another meaning I'm not aware of? Do you mean inverters?
AFAIK in an electrical context, choppers were devices to rapidly interrupt DC so that thyristors could be used (and are obsolete now GTO thyristors are available).

There are two main kinds of wind turbine: synchronous and asynchronous. The former turn at the same speed all the time (and when the wind's not blowing, normally consume a small amount of power to keep them turning as that's cheaper than restarting them). Asynchronous ones run at varying speeds. AIUI synchronous turbines used to be more common but aren't any more. I don't know what kind are used where in SA.

The load in a transmission network is inductive rather than resistive.

Victoria has plenty of spare capacity due to its connections to NSW and Tasmania.

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Craig, there's no advantage to shutting wind turbines down preemptively, though with hindsight it would have been sensible to put some gas turbines on hot standby.

I'm surprised a sudden change could stop the generation plant from working. Doesn't that mean a sudden shutdown of the interconnector would have the same effect?

ISTM the real problem is that the rapidly increasing load forced everything into an automatic protective shutdown when it really should have been counteracted by load shedding instead. Could load shedding be implemented sufficiently quickly? If not, to avoid a repeat of the problem, SA will need to install something to give the system more time to react. Asynchronous flywheel storage, maybe?

Yes Aiden, choppers is slang for inverters because that is how they work.
Yes same job as thyristors. Before that they used Ignatrons.
They must be old my Libra dictionary does not know the word.
What are GTO Thyristors ?
I was presuming that the turbines could be DC generators and the
synchronisation could be done from the mains supply and drive the
inverter into sync. Alternatively if they generate AC then the mains
could synchronise the m/c before putting it on line.
I also presume the AC ones have gear boxes.
Should be able to google all that anyway.
I recollect that the railways had mercury vapour, not ignatrons
another name, and they switched both ways so that trains coming
down the mountains could feed power back into the three phase mains.
Very impressive blue glowing light.
Must have been very dirty AC !

Yes Craig, I surrender, 30 deg.
Just been chasing three way rotor graphs.
Bit of revision on Google.

Aidan,

The AEMO (not the Australian) report clearly agreed entirely with the article in the Australian.

Wind power by its nature has far longer and exposed transmission lines than coal or gas power stations, and unsurprisingly it was those lines that failed first, this then overloaded the inter connectors which tripped, and the entire network collapsed.

If the coal power plants been running the inter connector trip may have been averted.

Bazz,

No, it wasn't very dirty AC, though ti may have been very dirty DC. Regenerative braking came early to some DC electrified railways, but AC electrified railways had to wait for thyristor based equipment to be developed.

GTOs are Gate Turn Off thyristors. Normal thyristors, once they're turned on by applying a voltage to the gate, stay on until the voltage across them drops to zero. GTOs can be turned off by applying a reverse polarity voltage to the gate.

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Shadow,
"If the coal power plants been running the inter connector trip may have been averted."
LOL!

While it's true that most of the gas turbine power stations don't have to rely on long transmission lines (as they're located in the Adelaide area) the coal fired power stations were both at Port Augusta. So they'd have exactly the same problem as the wind turbines.

Aidan,

The coal generator at Port Augusta were not only situated close to load at Port Augusta and Whyalla, but were joined to Adelaide by not one but several large independent power lines.

http://nationalmap.gov.au/renewables/#http://static.aremi.nicta.com.au/cec1.json&activeTabId=Legends

That transmission lines to wind farms tend to be more vulnerable was borne out in the report that clearly shows that the blackout was triggered by the loss of wind generated power.