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# Callide Power Station5

## Callide Power Station

(OP)
What is the likely cause?

CS Energy, which runs Callide Power Station Queensland AU), said there was a fire in one of the plant's turbines.

"That tripped the other three units, that then was a serious reduction to generating capacity in Queensland," CS Energy chairman Jim Soorley said.

The station was evacuated and a 550-metre exclusion zone put in place as fire crews worked to extinguish the blaze.

### RE: Callide Power Station

They say

https://www.abc.net.au/news/2021-05-26/queensland-...

Statements above are the result of works performed solely by my AI providers.
I take no responsibility for any damages or injuries of any kind that may result.

### RE: Callide Power Station

an oil leak from a bearing. even seaping between rotating shaft and oil deflector

Oil spray onto a hot turbine casing can also happen by other events

Local Power plant burned down to a test pressure gauge was left.

### RE: Callide Power Station

From reports, I have heard there was an issue with the generator circuit breakers on a turbine trip. Generator become a motor overspeeding the turbine until turbine blades let go. This is all third or fourth hand rumours so take what you will from that. My initial thought was hydrogen explosion but I now think that was secondary if it occured. I am surprised no pictures have emerged yet though. I wonder if a report will even be made public.

### RE: Callide Power Station

Synchronous generators cant overspeed when they motor, but unless the entire turbine casing gets pulled to a hard vacuum, it is easy to see the blade stresses would be wrong.
It is more likely the main steam stop valve did not shut when the generator breaker opened. That would quickly result in a rapid high energy disassembly of the turbine blades, and everything else nearby.

At the early stage of the investigation it is probably not possible to tell the difference between a hydrogen explosion initiated event and a rotating component initiated rapid disassembly followed by a hydrogen explosion. Once logs are examined it should be possible to discover which came first.

This was reported to be a really big bang.

https://www.news.com.au/finance/economy/damage-cau...

https://www.smh.com.au/politics/queensland/callide...

https://www.afr.com/companies/energy/queensland-po...

https://www.abc.net.au/news/2021-05-26/biloela-res...

### RE: Callide Power Station

just a little discription

The 900MW Callide Power Plant (Callide C) was commissioned in 2001. Callide C has two 450MW units. Toshiba supplied the advanced cycle steam turbine, and IHI the boiler.

a turbine generator operation at full power, if the generator breaker opens with a failure of the turbines steam valveS,
It will accelerate to destructive overspeed ~130% in about 3 seconds.

think of driving car, going up hill with gas pedal to the floor. Then, while keeping your foot down, put car in neutral,
the engine will accelerate to redline!

If they think H2 was the initator, the rotating element of the Generator is cooled by the Generator casing pressurized with H2.
Operating an unit with leaking H2 happens a lot. the migigation is to provide ventalation to prevent a flamable concentration to accumulate.

H2 explosions happen very quick (compared to blasting explosive)

### RE: Callide Power Station

I can't believe how that Energy Minister let that reporter herd him around like a fool making him cough up promises and guarantees.
What a tool.

Keith Cress
kcress - http://www.flaminsystems.com

### RE: Callide Power Station

Keith,
Even from afar, you have summed up Mick de Brenni quite accurately. He is just a Labor Party hack, with a history of being in charge of debacle after debacle.

https://www.couriermail.com.au/news/opinion/peter-...

### RE: Callide Power Station

The unit (CPP 4) had ramped down from 400MW output to roughly 280MW from about 12:00 to roughly 12:45, and maintained that until it ceased output at 13:55 (CPP 3 Tripped at 13:50 according to NEMlog). CPP 3 had been ramping 280 up to 430MW at the time it tripped out.

GCB reportedly stayed shut, only solution was opening the yard breakers tripping Callide B units and ultimatelly Gladstone (14:15 according to NEMlog.

### RE: Callide Power Station

Thanks hokie66.

Pushy news anchor pointedly asks, "Can you guarantee there won't be anymore power outages?"

He responds, "This is a very rare event on our newer plant, so no, there will be no more outages."

The guy doesn't even know what caused this one!

Keith Cress
kcress - http://www.flaminsystems.com

### RE: Callide Power Station

Incident was at unit C - https://youtu.be/D1-39kBq5gU

Callide Power Station Unit C3 major overhaul - 2019 PR Video

Hydrogen leaks should not be tolerated it is just too risky

#### Quote (https://en.wikipedia.org/wiki/Hydrogen_safety)

Mixtures

"The flammability limits based on the volume percent of hydrogen in air at 14.7 psia (1 atm, 101 kPa) are 4.0 and 75.0. The flammability limits based on the volume percent of hydrogen in oxygen at 14.7 psia (1 atm, 101 kPa) are 4.0 and 94.0."
"The limits of detonability of hydrogen in air are 18.3 to 59 percent by volume"[6][7]
"Flames in and around a collection of pipes or structures can create turbulence that causes a deflagration to evolve into a detonation, even in the absence of gross confinement."

(For comparison: Deflagration limit of gasoline in air: 1.4–7.6%; of acetylene in air,[8] 2.5% to 82%)

### RE: Callide Power Station

(

#### Quote (MDEAus (Mechanical) 27 May 21 05:28)

(CPP 3 Tripped at 13:50 according to NEMlog).
CPP 3 had been ramping 280 up to 430MW at the time it tripped out.
GCB reportedly stayed shut,
only solution was opening the yard breakers
tripping Callide B units and ultimatelly Gladstone (14:15 according to NEMlog.

Only speculation and wild ass assumtions

1) to prevent a turbine generator from accelerating to destructive overspeed, protection logic should have physical verification that turbine steam admission valves (Stops & Controls) are closed in a configuration to stop steam flow, with the addtion of verify generator "reverse power" and a time delay following);BEFORE the Generator Circuit breaker opens.

if valves are only stuck, partially open, without going reverse power, upon seperating the generator from its load, the turbine will creep to destructive overspeed.

during my years the verification of valve closed was the gruelly physical task of adjusting (and mantaining limit switches. during my waining year, the discussions for "upgrading" turbine controls considered deleting the physical limit switches and instead use the position insturmention.

the above discription sounds very much like the beginning of training classes for turbine controls

2) recovery following an overspeed event will take more than a couple weeks

### RE: Callide Power Station

The NRC produced a report (attached) on a possibly similar event. The results of an overspeed event are scary.

#### Quote (Attached NRC report Salen Unit 2 overspeed)

On November 9, 1991, a turbine overspeed event at the Salem Unit 2 nuclear power plant caused extensive damage to the turbine, generator, and main condenser. The turbine over-speed event resulted in a hydrogen explosion and fire, as well as lube oil fires.
Although there was no loss of life or personnel injury, the event resulted in property damage and a 6-month plant shutdown.

The turbine generator oversped to an estimated 2900 rpm (about 60 percent above the design of 1800 rpm). The shaft vibrated severely and turbine missiles (blading) penetrated the 1-1/4 inch-thick carbon steel turbine casing, making two elliptical holes on one side of the turbine casing. Each hole was between 15 and 20 inches across (see Fig-ure 4). There were also two tears 2 to 3 feet long at the same axial location on the other side of the turbine.

Some missiles landed over 100 yards away from the turbine. (Note that the turbine is located on the roof of an open structure.) One part of the turbine casing (about 15 inches by 20 inches by 1-1/4 inch thick) flew over the moisture separator-reheaters, and landed on a truck about 40 yards away. The low-pressure turbine was destroyed (see Figure 5). About 100 condenser tubes were cut by turbine blade shrapnel, and about 2500 condenser tubes had to be replaced (see Figure 6). No missiles penetrated the CB.

The high shaft vibration caused the mechanical seals from the hydrogen gas system (used for generator field cooling) to fail. The hydrogen gas was released, and it ignited. There was a hydrogen explosion and a hydrogen fire. The generator was severely damaged and it had to be replaced.

The vibration broke the generator bearing seal oil supply line and the oil was ignited by the hydrogen fire. Seal and turbine lube oil spilled into the turbine building basement.

We see hints of similar damage in the current event. The impact of the COVID driven supply chain trouble may result in a longer outage.

### RE: Callide Power Station

#### Quote (byrdj)

Only speculation and wild ass assumtions

1) to prevent a turbine generator from accelerating to destructive overspeed, protection logic should have physical verification that turbine steam admission valves (Stops & Controls) are closed in a configuration to stop steam flow, with the addtion of verify generator "reverse power" and a time delay following);BEFORE the Generator Circuit breaker opens.

if valves are only stuck, partially open, without going reverse power, upon seperating the generator from its load, the turbine will creep to destructive overspeed.

during my years the verification of valve closed was the gruelly physical task of adjusting (and mantaining limit switches. during my waining year, the discussions for "upgrading" turbine controls considered deleting the physical limit switches and instead use the position insturmention.

the above discription sounds very much like the beginning of training classes for turbine controls

I need a refresher on Turbine controls! I only had a 3 month stint at a local coal power station as an undergrad.

With a 'reverse power' situation is that likely to speed up or slow down the turbine? I could see how a stuck steam valve would overspeed once the generator load is removed. The generator 'reverse power' situation is a little less intuitive.

### RE: Callide Power Station

Reverse Power is "motoring" the turbine with the generator.

when connected, the generator is synchros with the Grid (and the units remaining on grid
so when the valves go closed, the turbine "wants to" coast down, but the generator motoring holds speed at that of grid. Normally that would be "rated", but when a major disruption occurs, who knows. In this case the grid might even be no other units attach, thus similiar to breaker open in effect not being motored

motoring is sort of OK for generator, but can be bad on turbine as it no longer has stem flow to keep the turbine rotor "cooled" (cool being at running tempurture) so MOST turbine should only motored a minute or so max

### RE: Callide Power Station

I think I read somewhere along the line they had to deenergize a large portion of the switchyard. That would suggest maybe a generator breaker didn't open when it was supposed to.

=====================================
(2B)+(2B)' ?

### RE: Callide Power Station

h'mm

turbines coasting down and things going bang

Chernobyl........

### RE: Callide Power Station

2
I think we've just landed on the engineering equivalent of Godwin's law there.

A,

### RE: Callide Power Station

^ or 6 degrees of 737-800

### RE: Callide Power Station

Large steam turbines often schedule "fast valving" of the IP turbine intercept valves, alternately closing one then the other at part load , to ensure that corrosion products do not cause these fast acting valves to stick open. If the unit had a steam to reheat bypass system, it is possible that such an excercise had led to a stuck intercept valve, which could have oversped the turbine. Don't forget that 80% of the steam turbines power is generated across the IP+LP stages.

"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick

### RE: Callide Power Station

I suppose the company ha obligation to release preliminary investigation report in three days or so. Can some one clarify on that please!!

### RE: Callide Power Station

I was hoping the Fire Fighters might leak some photos.

### RE: Callide Power Station

Indeed! That's a bad deal. Same thing the USA is letting happen in rail cars and e-buses.

Keith Cress
kcress - http://www.flaminsystems.com

### RE: Callide Power Station

Funny... Australia and the US have nearly twice the per capita carbon footprint that China has... might be something else...

https://en.wikipedia.org/wiki/List_of_countries_by...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

### RE: Callide Power Station

What is your point, dik? Do you want to live under the Chinese system? And while you were at it, why not include Canada in your list?

### RE: Callide Power Station

Nope... but a person has to be careful about pointing fingers... three of the fingers on the hand are pointing back at the pointer...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

### RE: Callide Power Station

I'll use my whole hand to point, then. But still want to know what your meant by "something else", and indeed how carbon footprint relates to China's attacks on the Western economies.

### RE: Callide Power Station

#### Quote (CEO Andrew Bills, CS Energy 01 Jun 2021)

Unit B1 will be returned to service on 11 June...
B2 on 21 June...
return date for C4 of 12 months’ time.

I would expect damages to the other, in service, turbine/generators during the "Black" coast down. one possiblity would be inadaquate cooling bearing oil, either while spinning down or sitting while hot. (sure there is balance of plant equipment that might also have suffered)

### RE: Callide Power Station

They're stating the re-start dates. Do we even know why the unit blew?

Keith Cress
kcress - http://www.flaminsystems.com

### RE: Callide Power Station

This is a screen clipping from the below video, bottom right is the HP IP turbine then in the centre is the LP and then on the left is the generator.

https://youtu.be/qEWAFgxRXa0?t=26.

Turbine hall was evacuted before the incident, by reports due to the "turbine not sounding right" and "overheating" according to un-sourced claims in the AFR.com artlice below

https://www.afr.com/companies/energy/inside-the-ca...

### RE: Callide Power Station

That shaft and coupling broke and were tossed out into the concrete sinking a foot into it. Seems more like maybe it went radically out of balance causing the shaft to fail.

Keith Cress
kcress - http://www.flaminsystems.com

### RE: Callide Power Station

A radically out of balance condition could include loss of baldes. The HP turbine location looks a bit battered.

There are some bright spots in the roof that are not light fixtures, possibly holes resulting from flying parts.

### RE: Callide Power Station

TBF that looks like a concrete cover over some sort of void, but a big bang for sure.

It's not going to be generating any electricity for quite a while, if ever.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

### RE: Callide Power Station

#### Quote (MDEAus (Mechanical) 2 Jun 21 06:53)

...before the incident, by reports due to the "turbine not sounding right" and "overheating" ...
I wonder what the generator MW output before incident. (also what they were doing)

I can think of two conditions that could cause "funny sound and overheating".

If there was a lost of condensor cooling allowing back pressure to increase will overheat the long last stage buckets. an increase in temp will cause them to be thrown off. the gen end of the LP hood looks missing, but I would expect hood to have more damage.

discription of plant state the steam cycle was "advance". IF it incorperated HP/IP by passing steam for quick start to hot unit, there should be "cooling" steam going through HP/IP as LP is used to roll the genenrator, failure of that valving arangment would over heat te HP/IP and cause rotating and stationary to try and "lock-up"

the damage to HP/Ip seems concealed by the extremely damaged lagging.
I can't tell if the piece of the coupling embeded in concrete is A or B (between IP and LP or LP and generator)

assuming the initation was a mechanical failure of turbine, the fire would have started when the bearing cavities were torn apart. the following loss of oil pressure would defeat the generator shaft seals allow 60 psig H2 to be blown in to the oil fire

looking at the torn off end of the couple reminds me of a remotely possiblity would be grid torsional vibration causing the shaft to crack and eventially shear.

### RE: Callide Power Station

Not a concrete floor but a steel grid mesh floor, not enough spalling for concrete floor, during overhauls they cover with ply wood. Highly energetic failure for sure though, LP and generator didn't suffer like the IP HP side.

I bet the person who ordered everyone out of the turbine hall is glad they made that decision. Usually work this incidents it's questioning why people weren't evacuated.

Given that the generators casing is largely intact that would seem to rule out hydrogen explosion? If it was an issue with hydrogen leaking into the LP turbine through severe vibration it would detonate the LP turbine.

300kg debris craned from the turbine hall roof. Wonder how far debris spread. There are a few new sky lights.

### RE: Callide Power Station

Gen output according to NEMlog was approx 280MW, they had ramped down from 400MW as per an early post. Power state had been pretty steady at 280MW then it had an unplanned disassembly.

### RE: Callide Power Station

I haven't been able to sort through NEMlog, BUT found this in another forum post
If I read it correct, it appears unit C3 dropped load prior to C4 (might be plotting squew due to sampling rate)
the C4 reduction (and c3 increase) had only occurred an hour or so prior Looks like B was able to ride excursion for a few minuts

### RE: Callide Power Station

I think you are right about the sampling rate squewing the plot, although it would still be interesting to see why Unit C3 still tripped first even if only fractions of a second(but due to polling rate of data it's logged as 5 minutes earlier).

Either fire fighting/electrical safety would have been the reason for B2 to trip. If GCB remained stuck closed after the turbine disintergrated then fire fighting would have been hammpered due to safety. Yard breakers may have been the only way to safely de-energize everything?

### RE: Callide Power Station

Actually judging by the frequency plot it appears that C3 did trip off before 13:45 sending the frequency through the floor (as lossing 400MW would do). C4 didn't have a much effect on the frequency after droppping out. Still 4 to 5 minutes between C3 tripping and C4 ceasing to exist.

### RE: Callide Power Station

#### Quote (Colin Boyce MP - Member for Callide facebook Yesterday at 3:43 PM)

...I have been informed that this devastation is the result of a hydrogen explosion inside the generator which has led to the destruction of the generator and the turbine shaft in C4...

explosion of H2 in a running generator are rare. Unless the operators let the purity go to hell. A funny noise could have been a loose bar or shorted turn that eventaily cause a ground fault. then the generator "braking" far exceeded its load and rung the coupling off

maybe posible that the generator shaft seals were blowing by, bearing cavity filled with H2/air mixture, then a spark from the grounding bush/braid strap. wipeing the adjacent bears, locking up the inboard gen bearing

very interesting that is seems the AU politicians are more envolved with the operations of power plants

### RE: Callide Power Station

#### Quote (byrdj)

AU politicians are more envolved with the operations of power plants

Because in Queensland they are state owned. Other states have done 99year leases but Queensland for various reasons didn't, even though we started down the path of privitisation(starve for funds, and split into smaller companies).

### RE: Callide Power Station

AEMO Prelim report

I don't think anyone had posted it yet.

13:34 Unit 4 stops generating power while remianing connected to the power system(first big drop in frequency on the above graph)Generator starts drawing approx 50MW and 300MVAr.
13:40 CS energy report turbine hall fire.
13:44 C3 Trips (second big frequency dip).
14:06 Calvale Yard breakers are triggered. Dropping B2 of the grid triggering the cascade of other units, Total generation capacity lost 3045MW( I don't think all units counted here were at capacity so this is total potential capacity)

Anyone know what 32 minutes of a generator motoring will do? Especially with fire for approx 26 minutes.

Lot's of talk coming out of places with the usual "I didn't tell you nuthin". Workers being pressured not to "speculate" on cause of incident.

### RE: Callide Power Station

MDEAus,
"Given that the generators casing is largely intact " - I was told that the generator casing is constructed to withstand H2 explosion and I think that's what we are seeing (End shield failure but the casing intact).
32 minutes of motoring - Even a few minutes of motoring could cause end stage LP turbine blade expansion that leads the blades rip through the LP turbine casing. Motoring protection is set generally with a couple of seconds delay.
Seems the machines didn't have Breaker fail protection as a back up to Generator Circuit Breaker (GCB) failing to open. There may be no instruction (in the operating procedures) for the control room operator to take action in the event of GCB failing to open on protection.

### RE: Callide Power Station

Tip clearances are small at running temperatures. LP blades get rather long. If the turbine steam stop shuts, flow through the turbine will fall to a low value, so the blades are likely aerodynamically stalled. Considerable windage friction will result. If the motoring load was 50MW, a significant amount of that is heat input to the turbine.

Loss of steam flow likely results in a loss of vacuum, which aggravates the windage friction.

Turbine heats up, blades expand and start rubbing the casing.

### RE: Callide Power Station

I'm not well versed in Generator electrical failure modes.

would it be that the generator had a bar to ground failure, thus sucking in the 50MWs. the "explosion" in the generator was initated by the BIG arcing and then release of H2 (by blowing out the seal casings, leaving end shields intack) then the blast of H2/air.

I didn't notice the seperation of the turbine from generator (by sheared coupling) in the sequence. maybe for that "motoring" period it was just current to ground (with generator field LOCKED)

thinking about it in this context, I can see that the design of the H2 seal oil casings could be a "relief" blowout, thus endshields and casing not being damaged

as implied by other, motoring of generator is not all that bad. Spinning a turbine (by motoring) with out "cooling" steam flow is real bad

notice the hood relief diaphragms look like they blow with a lot of force. I think they are design to blow if condesor goes 1 bar positive pressure

My first assignment (4 decades back) was the return to service of a generator that had a bar explode (loss of water coolant) but I did not remember the symptoms that occured during failure

### RE: Callide Power Station

#### Quote (Colin Boyce, the state LNP member for Callide,)

..., told CQ Today he had been informed by people on the ground that a hydrogen bearing seal failure was the cause of the breakdown.

“The reasons behind the generator and turbine failure at Callide C 4 are reasonably well-known in closed circles,” he said.

“Just very briefly, there has been a hydraulic bearing seal failure, which has led to hydrogen leaking from the generator, which has led to an explosion, which has led to generator failure and turbine shaft failure.

Looking at the generator wrapper, I am assuming that Toshiba might have the GE type dual ring design with once through treated seal oil

### RE: Callide Power Station

#### CODE --> boyce

reasonably well-known in closed circles,

What I am hearing from these closed circles is slightly different to this but I've been asked not to share as they have been told not to "speculate", not to say that this couldn't have been the reason for the explosion but it might not have been the root cause. The question is why did the seals fail?

That whole post is pretty much just playing wedge politics. Colin Boyce is the federal LNP memeber for that region. The QLD state government is Labor, much of the post will be politicking and slim on details. The LNP have been trying to get new coal generators built for a few years, Labor are resistant to that but also trying to appear sympathetic to coal miners. Note both take huge donations from coal mining companies. Just a bit more background info on the politics involved.

### RE: Callide Power Station

(MDEAus)
from what little is available, it seems the other units have not returned to service.
Has there any public info on why such a long delay. best case, I would have though a couple days cleaning coal handling from the abrupt stop.

However, Damage from insuficeint bearing cooling oil (battery time on DC oil pumps)

I

### RE: Callide Power Station

Insufficient bearing cooling oil is a well known troubleshot.
During the 1965 NY blackout
Northeast blackout of 1965 The newly placed into service unit 30 (990MW) was damaged (no lube oil supply to the bearings resulted in serious wiping of the bearings), and out of service for many months. The lube oil system was powered only from utility power, and had no reserve power for black spin down.

Perhaps the station designers made the same mistake, and assumed complete loss of station power was not credible, or did not include enough battery for the entire coast down? Spinning down a large generator can take a many hours?

There are other ways an unsupervised trip can cause damage to large units. With the plants being evacuated, all sorts of things are possible Energy and Power - Important Guidelines To Startup and Shutdown a Large Generator

### RE: Callide Power Station

"Big Allis" at Ravenswood.

the folklore was that operator instructions was to place the hot unit on barring gear asap. However when DC oil pumps ran out and with no heat removing oil flow over the stopped journals, the bearing babbit went plastic. So when AC power came back the attempts to put units on gear wiped the bearings. However the iceal of running oil pumps alone for several hours following such an event before TG was not pushed.

Also excessive force assisting barring damaged the close tolerance between bucket tips making contact due to rotor bowing again waiting more hours (day) for thermal equilization

### RE: Callide Power Station

The investigation is to be wide ranging, including human error. It is my understanding that there is uninterruptable power supplies to the oil pumps, if these failed or something in this system failed will be part of the investigation.

If the hydraulic oil pumps for both C units ran off the same UPS, then I could see why C3 tripped of first and why it would now take months to return to service if the UPS failed and subsequent loss of oil flow caused bearing damage.

### RE: Callide Power Station

Just guessing and rambling here . . .

The prior designs similar to that turbine would have had a shaft driven oil pump. even though centrifugal, it would provide oil pressure / flow during coast down to about 1000 rpms. And as the shaft pump decade, a DC emergency bearing pump would sense and start to provide for the rest of the coast down. AND with the lost of vacuum, the rotors would coast to stop in about 45 minutes (or less).

So, turbine / generator could have been designed to coast to stop with no AC. However, the batteries for DC are only recommended to provide for coast down. And stopped with HOT rotors, the bearings will get hot shortly with no oil flow

Even farther, the plant could be design to survive a loss of switch yard and the turbine generator stay spinning providing “House” power. The latent heat in the tripped boiler could provide enough steam for operators to do boiler purge and get flames back in (30 / 45 minutes) . been there, seen that!

If 3 and 4 shared a control room, I expected to operators were concern for their life and not the grid

### RE: Callide Power Station

In marine, oil pressure comes from a head tank that provides a minimum of 5 minutes of pressurized oil flow. We do also have the luxury of an astern turbine capable of shaft bursting which lets us bring things to a stop quickly.

Our feed pumps are also steam powered so s long as the boiler is hot enough to damage itself it's hot enough to keep itself cool.

Secure fires and open the superheater vent covers 90% of the fault responses.

### RE: Callide Power Station

Yes I believe these turbines have shaft driven oil pump and a back pump. I am not sure what it would take for both of those to be offline.

### RE: Callide Power Station

Even at a few rpm, the turbine still requires pumped oil. A turbine spinning at a few rpm is neither capable of producing electricity to run the electric pumps nor provide sufficient speed to maintain oil pressure with the shaft driven pumps.

### RE: Callide Power Station

From the AEMO Preliminary Report all the Feeders into H24 Calvale opened at their remote ends at 1406hrs (ie. at Halys, Wurdong and Stanwell on Zone 2 Protection. This is what disconnected the faulted unit from the system. No CBs in H24 Calvale opened, None.

See this AEMO Preliminary Report: https://www.aemo.com.au/-/media/files/electricity/...

This indicates to me that All protection in H24 Calvale switchyard may have been inoperable. The following is a little out of the box thinking, but, according to NOAA models, “a combined CME is (was) forecast to hit Earth’s magnetic field during the late hours of May 25, potentially sparking G2-class geomagnetic storms.” The CME occurred on Sunday 23rd May and it takes a known time for the solar wind to arrive at the ionosphere, but they gave a broad timeframe so their forecast could be out by an hour or so. A CME induced Geomagnetic Storm could render the protection systems at H24 Calvale and maybe many other substations inoperable due to saturated Current Transformers from the DC flowing on the HV Transmission Lines.

Generator Transformers which are configured from 3 x Single Phase Transformers connected externally with a Earthed Star as a 3 Phase Unit are the type most affected by DC Saturation of the Magnetic Circuit. Callide C3 and C4 units are of this formation so they are susceptible to Geomagnetic Storms. Generator Transformer Core saturation could have caused the damage to the unit by indiction of severe 2nd and 3rd harmonics. I do not know what type of Generator Transformers are used for Callide B1 & B2.

The start of the problem as seen by AEMO via SCADA was Loss of Power Output by C4. Harmonics could have caused the shaft to fail between LP Turbine and Generator which would have caused the LP Turbine to be destroyed leaving the generator spinning on line. The piece of shaft on the floor looks like the end pointing upwards has been rubbing against the other part of the shaft spinning at a slower speed and eventually stopping. The interference between the shaft sections at the break would eventually cause damage to the bearing supporting the generator shaft and throw out the section of shaft.

There also seems to have been a failure of electrical protection systems on the generator because it did not trip from Reverse Power. The Generator 20kV Breaker did not open and the Backup Reverse Power inter trip should have opened the 2 x 275kV CBs in H24 Calvale so there seems to have been serious protection problems at H24 Calvale.

### RE: Callide Power Station

With reference to the Frequency graph supplied by ByrdJ, the the yellow, purple and red traces are the AEMO Dispatch Targets for C3, C4 and B2 Units respectively. These only change after a trader rebids the unit after it trips or when the spot price changes the target. It does not record the actual time of the unit trip, only the time the rebid entered the dispatch calculation in 5 minute intervals. The frequency trace shows when the trips occurred. Unit C4 reduced generation to reverse power at 1334hrs, Unit C3 tripped when C4 lost excitation at 1344hrs and Unit B2 was disconnected from the system at 1406hrs with the disconnection of the 275kV feeders from Halys, Stanwell and Wurdong at Halys, Stanwell and Wurdong.

I have some more information about the Geomagnetic Storm but I have lost the links to the website so I dare not include them here. Suffice to say that careful examination of the graphs shows that the incident occurred in the middle of the Geomagnetic Storm which lasted for about 8-9hours. Coincidence! maybe. Cause? The storm presence extended from Sydney to Townsville, lying directly along the path of the HV Transmission lines from Bayswater to Townsville.

If I can find the link to the information I will post it on this thread.

Ian.

### RE: Callide Power Station

Any details as to what led to Substation busbar trip??

### RE: Callide Power Station

I notice they hired this guy Dr Sean Brady to investigate. His published investigations make interesting reading. He sounds like a good choice for a lead investigator.

### RE: Callide Power Station

If so, soon we will have an informative report from Dr. Sean Brady I suppose!

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