WHILE the storm that hit South Australia yesterday, Wednesday 28 September, was large and intense, the winds do not appear to have been particularly severe – at least not relative to what we often experience in northern Australia. For example, a Category 2 cyclone has wind gusts of at least 125 kilometres per hour. According to ABC online news reports gusts reached 83 kilometres per hour in South Australia causing the entire state to black-out. This is the maximum speed that I can find at the Bureau of Meteorology website for Ceduna, which is on the South Australian west coast.
![[image courtesy of Christian Kerr on Facebook]](http://jennifermarohasy.com/wp-content/uploads/2016/09/AdelaideAchievesZeroEmissions-1-300x300.jpg)
Nevertheless, this is still much less severe than would typically be experienced during a northern Australian cyclone, with the Queensland electricity grid withstanding recent cyclone Marcia (156 km/hr) and even Yasi (285 km/hr gusts) – though there was local damage and power outage.
The Australian Wind Alliance has issued a press release this morning stating that, “South Australia’s wind farms were pumping nearly 1,000 megawatts of energy into the state’s electricity system before yesterday’s mega storm tripped the network.” Specifically 960 megawatts at 4.30pm, covering around 50% of the state’s demand, and that the system failed because “23 transmission pylons” were “knocked out”.
I understand that the particular wind turbines common in South Australia cut-out at 90 kilometres per hour. So, it is plausible given: 1. readings from the Bureau website show wind gusts did not reach 90 kilometres per hour; and 2. data showing wind energy production for South Australia fluctuated between 1200 and 900 megawatts until 4.30pm when it dropped to zero – that the problem was the storm taking out transmission pylons rather than a failure of the wind turbines per se.
Nevertheless, this is unacceptable: the transmission pylons should have been built to withstand much more severe weather events.
UPDATE – 5 OCTOBER 2016
The Australian
Michael Owen, SA Bureau Chief, Adelaide @mjowen
South Australian Premier Jay Weatherill’s insistence that last week’s statewide blackout was wholly related to severe storms has been cast into doubt by the release of a preliminary report by the Australian Energy Market Operator, which shows there was a reduction in wind farm generation at connection points leading up to the outage. The report said more analysis was required to determine what that cause was.
A summary of the AEMO interim report said the storms caused multiple transmission system faults, including the loss of three major 275 kV transmission lines north of Adelaide in the space of 12 seconds.
The report said generation initially flowed through the damaged systems but “following an extensive number of faults in a short period [seconds], 315 MW of wind generation disconnected”.
“The uncontrolled reduction in generation resulted in increased flow on the main Victorian interconnector to make up the deficit,” AEMO said.
This resulted in the interconnector overloading and an automatic-protection mechanism tripping the interconnector to protect it from damage, causing the rest of the state to go black.
… A transmission tower carrying power lines was toppled by high winds near Melrose in South Australia during the storm.
… The AEMO investigation found that the uncontrolled disconnection of 315MW of wind power “increased the flow on the main Victorian interconnector (Heywood) to make up the deficit and resulted in the interconnector overloading”, he said.
“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.”
“That is not how the electricity system should be operating and the Premier has been badly exposed by this preliminary report… ”
The report can be downloaded here: https://www.aemo.com.au/Media-Centre/-/media/BE174B1732CB4B3ABB74BD507664B270.ashx
Jennifer Marohasy BSc PhD is a critical thinker with expertise in the scientific method.
Jennifer,
Surely 87 is close enough 90 that allowing for the errors in these figures, is it too much of a stretch to think that the windmills were very likely shut down?
Also do you have any idea as to how the mills come back online after being shut down through excessive wind speed?
Finally seems strange to me I cannot find a single image of the blasted towers.
Guess they cannot be so newsworthy after all?
Here is something that might let you appreciate what was involved:
http://www.abc.net.au/news/2016-09-29/restoring-power-in-sa-'very-delicate-affair'/7889846
Yunta is showing 113km/h at around 4.30pm yesterday and seems to be about the highest listed.
As for the towers collapsing with winds less than 100km/h, the designers must have been working to much lower standards than specified for buildings as far back as the 1970’s or they were negligent.
Maybe the interconnector was on the towers and they were not designed for that extra load rather than the slight winds.
Re : Wind Measurements – BOM vs Turbines.
The BOM sites measure wind at the standard height of the monitoring station.
The turbines measure wind at the height of the turbine, typically 50-80m AGL.
There is very significant wind gradient (ie lower layer speed loss due to friction with the ground) between those 2 heights.
Also turbines tend to be sited on hill/ridge tops or elevated areas to maximise their wind exposure and reduce the effect of wind gradient and terrain interruption to the airflow.
The often elevated terrain of those sites has the additional effect of compressing airflow to increase wind velocities even on light wind days.
The typically bare nature of the landscape where turbines are sited at also assists in increasing the wind gradient factors.
I suggest that the average and gust readings from the BOM sites are well below those measured at the turbines, in the order of 10-20% less.
Remember also that an increase in the speed of the wind increases its power by a square factor. eg: a doubling of 20km/h > 40km/h increases its power by a factor of 4. So what appears to be a somewhat small speed increase on paper during gusts – say 40>80kmh – quadruples the destructive energy. Imagine forces on the structures when the winds increase from 60>120km/h and above.
The force multiplier factor is why tornado’s cut paths through towns leaving an almost distinct line of destruction.
Clearly some very strong gusts hit the transmission towers and lines that went beyond their design limit. The colder humid air of the southern ocean storm has more density (and thus power) than its tropical counterparts, thus one can’t make direct comparisons to winds speeds between the two.
I notice on the ABC link that the power lines are still up. That seems a bit weird that the towers, that look like a kids meccano set, have toppled and the wires are still in the air
Thanks Bruce J. and also Godfrey, for that information. And you make a good point Lawrie.
what a joke – but not funny for households and businesses with no power.
wind turbines that can’t handle “too much” wind or towers that collapse under the force of the wind. What a total failure.
This hoax of global warming and dirty coal is costing all Australians hundreds or thousands of dollars every year because of inadequate alternate sources of electricity that are being forced into production by governments that have succumbed to the lies of the United Nations and the greens.
re start the coal fired power plant in SA and you can turn your lights back on.
I have little doubt this was the effect of an isolated tornado like phenomenon. It removes roofs in nearby Blythe [not Port Augusta], and I know that a similar kind of damage occurred to power pylons in a similar area some years ago.
South Australia gets isolated tornadoes that cause intense local damage from time to time. And is the want with a tornado – the wider area winds can be quite tame at the time.
On another note – the previous time also took out power but only for a restricted area because the network was more robust in those days. I think this is the point that needs to be established about renewables. They make the network more fragile and are pretty useless for recovery from a blackout.
Who is missing the point here; the wind turbines cut out (which they are designed to do so as to protect their structure) while pumping out half of the state’s power requirements. Hello??? The turbines cut out and took half of the state’s power in one swoop. Regardless of the problem with the towers, if the turbines cut out you have a serious problem.
HV Transmission lines are just that transmission lines and if SA didn’t have any redundancy in the transmission line grid then of course there will be no power especially when there they are relying on limited primary supply and little to no backup in the network.
Going a long way back, SA did do things on the cheap with transmission line towers, they used rectangular based “support” towers which did just that support the lines but couldn’t handle major side ways stress. However all the images I have seen show square based towers which are designed to handle loads far in excess of 80-90 km/h. Far north Qld transmission towers are known to fail in the high 200’s so not sure why a piddling 80-90 km/h took these out unless of course there was a localized micro burst?
Relying on 2 interconnectors from other states and wind isn’t really a good look. SA only closed Leigh Creek down this year as well as a number of their power stations in recent times so they did feather their own nest with this one.
If they were a proper engineering job the more wind the more electricity. They could balance the fans properly so they don’t shake the towers to pieces.does an aeroplane shake in flight or a car at high speed?. I think these things are unsightly junk. The political elites {academics) have certainly been conned by the UN and the scientists in their own interest. bit like the EU pre Brexit. They are laughing all the way to their Banks
The practical people suffer at their hands.
If the world had been left to the academics they would still be arguing over which end of the club to hold.
Ahhh! The irony is delectable:
The maximum operating wind speed rating for turbines is only about 35-40 kmh, not 90 kmh. Anyhow, the SA Power spokesman said there was nothing coming from any of the northern wind farms as they were all shut due to the high winds.
I suspect that what the Wind Alliance was referring to were the mini gas and diesel generators that are scattered around the Mid North to support the wind farms as they can’t start without getting either grid power or some of the power from these generators. However, they are not supposed to use this power for everyday consumption as it is too expensive and not reliable being from about 8-10 different generators.
Re Godfrey’s very useful comment:-
I wondered if V^2 was correct and checked at the following link:-
http://www.engineeringtoolbox.com/wind-power-d_1214.html
Unless I have completely misread the comment( quite possible at my age -87) the increase in power with wind velocity is the CUBE not the square.
Far from discrediting Godfrey’s comment it only supports it.
And if I have made a cock up I ask your forgiveness.
I would have thought lattice steel transmission towers would be built to withstand wind strengths of at least 60 m/sec [216 klm/hr] as many wooden poles are but maybe they only modelled them:
http://www.omicsonline.org/open-access/structural-analysis-of-lattice-steel-transmission-towers-a-review-2472-0437-1000114.php?aid=76086
Wind power is indeed proportional to the cube of the wind speed. Big wind turbines respond to average wind speed over a period due to the inertia involved. These turbines should be able to yaw out of the wind as the wind speed exceeds optimum, I.e. the turret gear turns the narcelle partly out of the wind. Specifications vary but typically40-60 kph is optimum and maximum output before yawing and 90kmh, at tower height is around the speed they’d think about shunting down. Not all turbines are created equal and there are many site specific variables as mentioned above. I have had some involvement with wind turbines but have not experienced a turbine in full flight that suddenly lost it’s grid connection. Even when these things yaw they become unpleasant to be near. An emergency shut down when under full power would be distressing for both machine and onlooker I imagine. I’d expect close inspection before recommissioning the plant.
I too am perplexed at the extensive failure of the pylons, especially in the goldplated investment environment of the past decade or so. I have no doubt wind power contributed to grid instability. To overcome these issues the whole system has to be beefed up, correcting power factor issues, conductor robustness and grid management. These things add to the hidden costs of renewables.
Re: Wind force on an object
Just to clarify for Lawrie et al : The base formula we use in aerodynamics is:
Kinetic Energy = 1/2 x Mass x Velocity squared
The KE of a parcel of air in motion relative to an object allows it to exert a force on an that object. When calculated per unit of surface area it is called Dynamic Pressure.
Air density (mass per unit of volume) plays a role in Dynamic Pressure so the equation becomes:
DP = 1/2 Rho V-squared. “Rho” is Air Density.
This is one of the most important equations in aerodynamics. Dynamic pressure is also more relevant than Kinetic Energy when discussing the effect of wind/air speed on objects both flying and fixed structures on the ground.
The “cube” factor Lawrie noted comes from wind “power” typically used for turbine calculations. The very same engineering toolbox website notes dynamic pressure using Bernoulli’s “square” function here : http://www.engineeringtoolbox.com/dynamic-pressure-d_1037.html
I hate wind farms (not isolated turbines) with a vengeance. They’ve despoiled the views in many of my favourite upland areas in the UK. Despite the density of population here, there are (were!) still many areas where the only outwards signs of human presence are a few stone walls or fences and some hill sheep; sometimes not even those. Large white whirley towers do not a view make, leaving aside their effect on birds and bats. Definitions:
Solar – most power when you least need it
Wind – least power when you most need it
Rant over, for the moment.
The pylons were built to service the windmills. Who controlled the construction standards, who executed the design of the pylons?
The story that the windmills were producing so much power and then went to zero doesn’t really hold up to scrutiny. If ground speed is 87 kph, then the wind at the blade height would have been higher. What is the impact of unreliable, highly variable power being put on the grid without proper conditioning? What is the impact of windmills having forced-buy ins of this sort of unreliable power on infrastructure choices?
@Hunter The four main power transmission lines through the mid north were probably actually built in the first place to carry electricity from three coal-fired power stations at Port Augusta south to the industry and housing around Adelaide.
We have returned to much of the state’s “base load” electricity being generated near Adelaide, so these connectors now operate the other way carrying electricity from Torrens Island and other nearby gas turbines north, supplemented by the wind farms they pass on the way.
Unfortunately when three of the four transmission lines fail, the fourth one overloads.
According to the latest, it was in fact the windmills, not the pylons collapsing, that triggered the black out. https://www.aemo.com.au/Media-Centre/-/media/BE174B1732CB4B3ABB74BD507664B270.ashx
Jennifer,
Thanks for posting the update showing that wind power, as skeptics have predicted, is going to not only cost consumers more in operating costs, but that wind power is also unreliable and a hazard to dependable electricity.
Thanks for the update.
How’s the rehabilitation to transmission pylon?
Are there damages to wind turbines?
The transmission towers have stood for 60-80 years. They have probably been through much worse storms.
I think that eventually we will find that the cause of the tower collapse was actually the shock of the shock waves initiated by the HV system protection.
When electricity is flowing it puts a stress on the lines similar to when you have water flowing through a hose.
If you cut it off suddenly then it whips around much like a hose does.
I will bet that this is what initiated the tower failure.
Were Gas Turbines and other back up power started up before the wind turbines that were supplying 50 % of the load reached their shut down / trip point is my first question
As a second question what was the spinning reserve power available for the total of whatever thermal power etc.
What also was being imported / exported on interstate links . There must be somewhere a sequence of events …. once that is identified then we can all see just what happened
Re : Wind Measurements – BOM vs Turbines.
The BOM sites measure wind at the standard height of the monitoring station.
This is true but all of the other factors, height, terrain category, direction are accounted for during the structural design by factoring up the wind speed from the 3 second gust design wind speed. Looking at the raw BOM data the storm looked to be a 1 in 25 year event. Houses are designed for 1 in 500 years and Level 1 infrastructure for 1 in 2000 years. PM J Gillard called this robust post disaster design gold plating when she wanted to blame things other than renewables for electricity price rises.
The difference between 1 in 25 to 1 in 2000 year events is of course not linear in terms of wind speed, however the wind pressure does increase to the square of the speed. In summary the towers should have survived pressures 50% higher than they collapsed at.