The real drama plays out in a 90 second window between 4:16:46pm and 4:18:16pm.
The weather triggers a series of transmission faults and three major 275 kilovolt lines are lost. Then, in two separate events, 315 MW of wind generation is disconnected. This unexplained, rapid loss of wind power is the event that begins the cascade towards blackout.
"In the events leading up to the SA region black system, generation reduction occurred at six wind farms," the report says. "There was no reduction in thermal generation."
Why it happened is still a mystery.
"Additional analysis is required to determine the reasons for the reduction in generation and observed voltage levels before any conclusions can be drawn," the report says.
Demand then shifts dramatically to the line with Victoria. Just before the wind generation failed the Heywood interconnector's flow was about 525 MW, well within its normal operating limit of up to 600MW.
The reduction in generation and the oscillations caused by the transmission network events drove demand to "flows between 850 to 900 MW" well in excess of its capacity. So it shut itself down.
Now the "non-credible" had become credible. At 4:18:15pm the door to Victoria slammed shut, draining 900MW of supply in a heartbeat. There was "a rapid reduction in the power system frequency" in South Australia and it "fell to zero". That tripped the two thermal power stations at Torrens Island and Ladbroke Grove and all remaining wind farms.
And the lights went out across the state.
It should be noted here that the report says that 14 of the 22 transmission towers that went down did so, "following the SA black system".
System had further flaws
In the eerie dark that followed the operator immediately began working through a pre-determined restoration plan. And that revealed more deficiencies in the system.
The operator has two contracts in South Australia for System Restart Ancillary Services (SRAS).Their identities are a secret for contractual reasons, so the report calls them SRAS 1 and SRAS 2.
Plan A was to use SRAS1 to jump start the thermal power station at Torrens Island and, at the same time, restore the interconnection with Victoria.
"This was seen as the quickest and safest way to restore supply to South Australia," it says.
In a footnote it adds, "wind farms cannot be used in the initial stages of a power system restoration due to the variable nature of their output".
Things didn't go well.
"Due to an issue currently under investigation, SRAS provider 1 was unable to supply sufficient capacity to restart any of the Torrens Island power station units," the report says.
SRAS 2 was out due to "damage caused by the storm".
Plan C was to hookup the interconnector with Victoria and use it to jump-start the state. By6:54pm Torrens Island was restarted but it needed another two hours before it could deliver any power.
At 6:36pm the operator was advised that the gas-fired turbines at Pelican Point could be ready in four hours. Here, it's worth noting that gas plants can't just spring into action ? they need time to warm up. Pelican Point had been off-line before the storm, bid out of the market by cheap, abundant wind.
SA power system 'extremely fragile'.
So what have we learned ?
That weather sparked a series of events that spiraled into a state-wide blackout. That it was the sudden loss of wind power that tripped the interconnector with Victoria and that loss of generation is yet to be explained.
It is also undeniable that South Australia now has an extremely fragile power system. It cannot operate with any confidence if the interconnector with Victoria is down and if the state blacks out it can't be restarted with wind power.
Politicians have said a lot of things in the wake of this outage. But judge them by what they do. South Australia is already calling for rule changes in the national electricity market because it recognises its reliance on wind and rooftop solar has made the state's system less secure. This won't be the last fix that South Australia will need to patch up the problems.
Finally, we know that the energy market is in transition to cleaner forms of power and that is unstoppable. In time the engineering difficulties posed by wind will be overcome. Or they will be as long as people aren't burned as heretics for daring to point out the real and well documented problems with integrating new forms of energy into an old grid. And, if those who claim to be friends of renewables continue to respond to any criticism with hysterics, then they will be responsible for ensuring the budding renewable industry suffers irreparable reputational damage.
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