Wednesday, Sept 28 2016 — Weather events caused a series of shutdowns across 50% of the state’s wind power farms, the Victoria to SA interconnector, and backup generators.
- 2 tornadoes destroyed 3 major power lines in South Australia.
- 5 system faults caused 6 voltage disturbances leading to 445 Mega Watts(MW) of power from wind farms to disconnect from the grid.
- 1826MW was being used on the grid in SA and within split seconds, 25% of that total power was disconnected.
- The shortfall in power fell onto the inter-connector, it attempted to draw 900+MW and a safety mechanism switched it off.
The SA grid started with 1800MW was then left with only 330MW — A 1500MW shortfall. That remaining 330MW was being generated by conventional power plants — mostly gas.
It’s also worth noting that South Australia — according to the State of the energy market report 2015, has 2000MW of gas generation capacity. That’s far more than wind capacity and gas power plants only take 30 minutes to start up.
So what really happened?
What the government said
The government was quick to lay blame on the South Australian Labor government for their inability to “keep the lights on”.
‘The South Australian blackout was precipitated by a weather event but what made the South Australian system a lot more vulnerable was its heavy reliance on intermittent and unpredictable sources of power,’ Energy Minister Josh Frydenberg told Sky News.
But emails released the federal government told a different story.
AEMO’s advice is that the generation mix (ie renewable or fossil fuel) was not to blame for yesterday’s events — it was the loss of 1000 MW of power in such a short space of time as transmission lines fell over,’ one email read, Fairfax reported.
Mr. Turnbull confirmed this later
‘Of course windmills did not cause a blackout. The blackout, as I have said many times, was caused by a storm breaching transmission lines,’ he said.
So was it intermittency or was it weather?
What AEMO said
The Australian Energy Market Operator (AEMO) is an independent company that operates the national electricity coast grid & gas lines.
They released 4 reports giving cause to the blackout.
The unexpected operation of the control settings resulted in the sudden loss of generation from the wind farms.
Like any electronic device, large disturbances in voltage can break them. Think circuit breaker. The wind turbines are designed to switch off under certain conditions. Those conditions were ‘unexpected’.
The two contracted SRAS suppliers both experienced difficulties in providing system restart services due to two separate faults.
In the case of a blackout, ‘system restart ancillary services’ (SRAS) are supposed to turn on backup generators to support the grid while it is restarted.
Even with these services faulting, 80% of the grid power was restored in 5 hours.
Had the generation deficit not occurred, AEMO’s modelling indicates SA would have remained connected to Victoria and the black system would have been avoided.
Since the incident, AEMO has tweaked the ride through software and so now the turbines are more resilient to voltage disturbances. They’ve confirmed in the same scenario this would not occur.
What scientist said
Australia’s Chief scientist Alan Finkel, said while there were challenges to incorporating high levels of variable renewables, there were ready technology solutions.
He also pointed out that the wind farm settings had been identified and solved in Europe a decade ago.
This view was echoed by a report from the CSIRO and Energy Networks Australia. Australia could, and should, aim for high levels of renewable energy — both for climate and environmental reasons and because it was cheaper.
The challenges Dr. Finkel is referring with renewables are 1) Intermittency 2) Inertia
1 — Intermittence is the rhythm of natural systems. Tides go in and out, the sun goes up and down, wind speeds change over time. It means we need to build oversupply, variation, and storage into the system. Not super difficult.
The best part is though these things are quite predictable, and did we mention they are renewable…
Fossil fuels, on the other hand, need to be dug up out of the ground and burnt. Seems like a fair trade off maybe?
2 — Inertia is the momentum of large rotors driven by steam or water from thermal or hydro power plants. Like a heavy car vs a light car, the heavy car tends to keep moving forward with more inertia than the lighter car — or pedestrian.
The weight of the rotor, spinning with the same frequency (50 times per second) as the alternating electricity, tends to maintain that frequency by way of its inertia — keeping the synchronous AC generator in sync with the grid AC.
Asynchronous generators from renewable sources are DC generators and do not have this inertia or even an alternating type current to sync with the grid. Synchronous generators were used before asynchronous generators and are a very old a well-understood technology.
Condensers are used to create electronically made inertia, acting between the power inverter and the grid, to prevent the frequency getting out of sync.
The federal government, AGL, AEMO and UNSW have all made models for Australia at 100% renewables. All work totally fine.
Sure it’s a mix; mostly wind, some solar, battery farms, some biogas, a bunch of other smaller things. But what’s wrong with diversity?
The current target is 20% renewable energy generation.
Is that enough?
Also published on Medium.