Hi and welcome to Failurology; a podcast about engineering failures. I’m your host, Nicole
And I’m Brian. And we’re both from Calgary, AB.
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In our last episode, we covered the first part in our wind turbine failure series. We talked about the most common cause of wind turbine failures, which is blade failures. We also talked about optimizing wind farms and how wind energy has impacted Alberta and Germany.
Yes, and we’re back for more wind turbine failure discussion with Leann, a mechanical engineer working in the waste-to-energy side of the renewables industry. She is coming to us all the way from Germany. And having worked on wind turbines at the beginning of her career, she’s teaching us a thing or two about how wind turbines work and how they fail.
To recap before we dive in. The wind turbine includes a foundation, tower, three blades, a nacelle which houses all of the mechanical components, a gearbox and a generator. As the blades spin from the wind, they turn gears in the gearbox which are connected to the generator to turn the mechanical energy into electricity. We’ve already talked about blade failures, next up we have generator failures.
Generator creates electricity by converting mechanical energy into electrical energy
When generator fails = no power
Common reasons for failure
Mech or elec failure of bearings
Cooling system failures
Manufacturing or design aults
Inadequate electrical insulation
Comprehensive maintenance and repair program will improve reliability and longevity
Fire failure at the Juniper Canyon Wind Farm in Klickitat county - south of Bickleton, Washington (home of the Bickleton Carousel Museum lol).
On 14:00 July 20 2019, something in the nacelle caught fire, spread to the blade which fell to the ground and caught grass on fire - the fire burned up 300 acres.
There were no reported injuries or structural damages from the grass fire. The
Juniper Canyon 250MW wind farm consists of 63 2.4MW turbines (100m diameter rotor) and 65 1.5MW turbines (not sure the make and model but probably ~70m diameter).
No report found on the fire incident (??). A fire in the nacelle would likely have started either at the mechanical brake of the generator or in the converter/capacitor cabinet.
The original Piet de Wit Wind Farm was composed of twelve 1.75Mega Watt turbines with a total wind farm capacity of 21MW and located in Ooltgensplaat(pronounce: Olt-Gen-Splat), Netherlands.
The turbines were commissioned in 2003.
On the afternoon of October 29, 2013 one of the turbines caught fire in the nacelle while four mechanics were doing routine maintenance. Two of the mechanics used their Constant Rate Descender safety devices to rappel quickly down the tower to escape.
The Constant Rate Descender slows the descent to 2 metres/second which is slower than one would land after hopping up on one foot. I assume these are similar to self belay devices at climbing centers.
The fire atop the 67m tower was too high for the first responding firefighters to reach. It is suspected the two mechanics still trapped in the nacelle were not able to reach the safety devices through the flames.
By the time specialty firefighting equipment arrived for a rescue it was too late for the two trapped workers; both men died as a result of the incident. The fire was extinguished later that evening.
The suspected cause of the fire was a short circuit due to a dropped tool. The employees had de-energized the voltage from the majority of the components prior to commencing work.
The remaining 11 turbines of the original Piet de Wit windfarm were decommissioned in 2021 and replaced by 7 new 4.8MW Nordex N133/4800 turbines for a total new capacity of 33.6MW.
Most don’t last more than 10 years, short of the 20 year design lifespan
1,200 gearbox failures annually (2020 article)
Bearings and gears make up 96% of the failing components within the gearbox
Gearbox is ~13% of the overall cost of the turbine
Dirty or water-contaminated lubrication
Improper bearing settings
Significant temperature fluctuations
Improper or infrequent maintenance and servicing
Transient loads leading to sudden accelerations and load-zone reversals
The town of Hornslet located on Denmark’s eastern side commissioned a wind park of five 600kW turbines in December 1996.
On the morning of February 22, 2008 - a repair team arrived at site to service the brakes as it was making strange noises.
During a routine inspection prior to February 22 it was noted that the gearbox was making an abnormal noise and it was planned for specialists to perform an inspection at a later date.
The morning of February 22 the brakes were repaired and tested. By the time the technicians were ready to bring the turbine back online, the wind had picked up considerably to 25km/hr gusting up to 50km/hr.
As the turbine was restarted a noise was heard from the nacelle and technicians immediately initiated the shutdown sequence.
Just then a large crash was heard from the nacelle and the tower started to shake violently and cables fell down inside the tower. The rotor stops turning abruptly and then starts turning again slowly at first.
The technicians at the base of the tower note that they have lost control of the turbine, the mechanical brake isn’t working and they can see the air brakes at the tips of the blades have broken off - they evacuate the area realising that catastrophic failure is inevitable.
The technicians notified police and contacted nearby neighbours and evacuated everyone within a 400m radius of the out-of-control turbine. The rotor continues to pick up speed, far exceeding its design limit.
After 2.5 hrs the blades collapsed, contacted the tower and shattered with pieces flying as far as 500m away. The tower buckled at the point of contact.
The top half of the tower broke off and fell to the ground. Fortunately nobody was hurt in the incident.
The investigation following the incident confirmed extensive gearbox damage - the high speed gear teeth were totally ground down. It is suspected that the loud noise heard during the shut down sequence was the gearbox failing. It is also suspected that the abrupt stop of the rotor caused the air brakes tips to break off.
The mechanical brake is located on the high speed shaft between the gearbox and the generator - so when the gearbox failed the mechanical brake was no longer connected to the low speed rotor.
The event was deemed to be a series of unfortunate events, no official corrective actions were assigned except to stress the importance of timely maintenance performed by qualified personnel.
Screggegah wind farm Northern Ireland - on the Murley mountain in County Tyrone - eight 2.5MW turbines on site were commissioned in 2011.
Around 9pm on January 2nd 2015 a turbine had collapsed at the Screggegah wind farm.
Nobody was hurt in the incident and the debris was confined to the wind farm site. The area was secured and the other 7 turbines were shut down as a precaution.
The wind speed at the time of the incident was around 35km/hr, well within the design of the turbine and yet some people reported that they saw the blades spinning out of control.
We didn’t find many details about the investigation but it was reported that they found a glitch in the blade pitch control system which allowed the rotor to go into overspeed condition.
The operators made several attempts to recover but were ultimately unable to bring the turbine back under control.
The operators did not travel to site and did contact landowners in the area to warn them of the situation.
Eventually one of the blades fractured and the entire tower collapsed under the momentum of a massively imbalanced rotor.
Once the glitch was identified, an additional protective measure was implemented on the remaining seven turbines at the Screggegah wind farm.
Several rigorous safety tests were performed on the other seven turbines before they were brought back online.
It was identified that the glitch was only applicable to turbines of the same generation from that manufacturer and we presume that the others (approximately 1600 turbines) in service also received the protective measure.
This was the first fault of that kind for this make and model of turbine. The local health and safety executive also requested that the wind farm operator update their site emergency procedures, especially in terms of procedures for notifying the public of imminent safety concerns.
On May 2, 2009 one of the turbines at the Tehachapi Pass wind farm spun out of control
Located north of LA off of highway 58 and San Canyon Fd intersection the Tehachapi wind farm is home to about 3,400 wind turbines producing over 700 MW of power.
The turbine that spun out of control was located about 1400 ft from the highway and as a result, the highway had to be closed. Which was a great idea,because it disintegrated a couple days later, leaving a turbine-less twister tower in its place.
The cause is unknown, but runaway turbines are typically caused by bad brakes or gearbox failure. And the only way to stop a runaway turbine is to wait for the wind to die down
Structural failure relating to the tower or foundation of the wind turbine
Has to take into account the weight of the turbine and components, but also the forces exerted on the turbine by wind, ambient temperatures, precipitation and other forces.
On Jan 19, 2018 a wind turbine in Chatham, Kent, Ontario buckled, collapsing from the centre
The turbine was one of 52 in the facility and had been running since 2011. The remaining 51 were shut down while the failure was investigated.
Failure of the tower itself is rare, but collapsing from the centre is even more rare. Investigators suggested it was a failure of the structure design, instigated by extreme load, but didn’t give much more information.
In June 2017 a wind turbine at Shannon wind farm in northern texas collapsed.
It was one of 119 turbines in the farm
Only the bottom portion of the tower was left, the rest lay on the ground.
The wind farm was shut down for a few days while they investigated the failure and a new turbine was eventually installed to replace the broken one.
A spokesperson said this was an extremely rare and isolated incident
On Dec 27 2009 one of the 20 wind turbines at Fenner wind farm in Madison Cty New York collapsed.
the 187 ton structure fell into middle of field
A formal report was never released but the forensic engineers did rule out shoddy construction and deficiencies in construction materials.
The company reinforced the remaining towers with 4-6 tons of steel and 10 truckloads of concrete
In May 2009 a 60m tall wind turbine in North palm springs crashed to the ground.
So there you have it, the most common causes of wind turbine failures. Whether they’re spinning out of control, catching fire, or falling over, getting a handle on why and how wind turbines fail and improving their design is a critical step in the diversification of our energy program. When the wind turbine isn’t working for whatever reason, it’s not generating power.
For photos, sources and an episode summary from this week’s episode head to Failurology.ca. If you’re enjoying what you’re hearing, please rate, review and subscribe to Failurology, so more people can find us. If you want to chat with us, our Twitter handle is @failurology, you can email us firstname.lastname@example.org, you can connect with us on Linked In or you can message us on our Patreon page. Check out the show notes for links to all of these. Thanks, everyone for listening. And tune in to the next episode where we’ll talk about the Boeing 737 Max. The plane with the “safety” system no one knew about.
Bye everyone, talk soon!