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Fatal Explosion At Russian Hydroelectric Dam
stadium writes "An oil-filled transformer exploded at the Sayano-Shushenskaya power plant in Siberia, destroying three turbines and bringing down the ceiling of the turbine hall, which then violently flooded. The dam itself did not sustain any damage. It is unclear how many people were killed, but with 12 confirmed deaths and as many as 64 still missing (all presumed dead), this is a serious incident. The huge transformer had enough oil in it to produce a three-mile-long oil spill slowly moving downriver. BBC News reports with three separate videos. The dam produces a quarter of the total energy of RusHydro (whose stock thus took a steep dive at London Stock Exchange) and also feeds the world's largest aluminum smelter. The damages will take years to repair."
Most likely what happened was what's known as arc flash.
Arc flash is when metal is vaporized due to difference in potential between two objects, like phase to phase, or phase to ground. It's very dangerous to us humans because we burn easily, and because the vaporized metal tends to fly outward in a shotgun pattern.
An electrical breakdown in a large transformer can cause this internally, and as the live power works its way from the inside out, it can vaporize holes in the transformer casing. So you have boiling oil, vaporized copper/steel/etc, and a lot of live electricity trying to get back to earth ground.
This is why electrical engineering is very important. All it takes to cause this is someone disconnecting or connecting a line under the wrong load, or with no load at all.
Job? I don't have time to get a job! Who will sit around and bitch about being broke and unemployed then?
http://rutube.ru/tracks/2264709.html?page=index_top_d&v=895630c2b1f248fafd957862a037d663
Somewhat off topic, but...
While true and oft-repeated, the volt/amp comment ignores the fact that there is a definite relation between the two. It is easier to determine the exact effect on the body if you know how many amps went through the person's heart and/or other muscles, but ballpark figures with volts can give some idea of the danger. The body is essentially just a resistor, so there is a linear relation between volts and amps if you know where that voltage is applied and thus what the resistance of the body between those 2 points is. You know that with 12 volts it takes some ingenuity to kill someone, but 120 volts from a wall socket is dangerous if mishandled. 1200 volts will be fatal when applied directly to the skin almost anywhere. 12,000 volts will not only kill you, it will arc through small air gaps to do so (i.e. tasers, you don't get all of the claimed thousands of volts over the body, most is dissipated across the air gap or is regulated by the circuitry to keep the current low).
The way I look at it, amps give you a good idea of how dead you are. Volts gives you a measure of how bad something is trying to kill you.
EnglishRussia.com has some pretty stunning pictures of the damage.
PCBs have not been used in transformers in the USA for more than thirty years. Not forgetting of course that this hydro plant was built 31 years ago.
TFA says the transformer exploded while being "serviced". A good wild guess would be they were welding on it and sparked some combustable gasses inside the case. (so it was probably partially drained at the time of the explosion) That air pocked inside the transformer would be an ideal condition for an explosion like that. Rapid expansion of gases inside an otherwise mostly sealed container like that would send multi-ton pieces of metal in all directions, it'd be like a giant frag grenade. You thought exploding batteries in DSLAM cabinets were bad, these are quite a bit worse.
As for age, there are PCBs in 1/4 of the trashcans on the poles today. Just because they don't manufacture with it anymore doesn't mean it's not still out there. Transformers are expensive, and I don't even know if you can change from PCB to mineral oil practically speaking. (it's gotta be hard to get PCB fluid out of saturated paper windings) BIG transformers like that are outrageously expensive and are only manufactured in a handful of places on earth, so much that price AND availability are problems when obtaining them. Odds of it being a PCB-containing unit are actually very high since big transformers are not only incredibly expensive but are also one of the longest life electronic components in existence. (they are also one of the most efficient)
I work for the Department of Redundancy Department.
Some types of transformer oil, break down to flammable gases when there is an internal fault. These faults result from such things as vibration wearing the insulation, or heat damage to the insulation. When the phase arcs to ground or phase to phase the usual by-products are hydrogen and acetylene. When the right concentrations are reached they explode. Most large transformers in the US have pressure sensors that try to de-energize the transformer when the gasses begin to build. This isn't always successful, and sometimes they explode. A large generator, such as a large hydro unit, next to the fault can cause the gasses to be generated very rapidly. This must be the case, as this is a standard precaution used for many years.
We can get by without gasoline; it will be an infinitely harder time getting by without plastics. As stated, most of modern medical practice is based on the assumption of cheap, sterile, disposable items (although I *do* hope a lot of that is recycled - biohazards melted away first, of course).
We can make plastics from corn oil. Not a problem. Most medical waste is incinerated, for obvious reasons.
by Mike Buddha -- Someday the mountain might get him, but the law never will.
- Dams stop natural sediment flow, resulting in downstream river erosion
- Fish breeding / migration
- Increased irrigation enabled by dams causes pollution of ground water aquifers (increased salinity etc)
- Methane released decaying plant matter in non-oxygenated stagnant dam water
The explosion is from arc flash when the coils in the transformer short. The metal explosively transitions from solid to a mixture of plasma, gas, and liquid. The surrounding oil is then atomized by the explosion and so creates a huge fireball. Depending on just how unlucky you are, you can also end up with a metal fire after that (which a standard ABC extinguisher will NOT put out).
> TFA says the transformer exploded while being "serviced". A good wild guess
> would be they were welding on it and sparked some combustable gasses inside
> the case.
That's a pretty good guess. Acetylene can form inside oil filled transformers.
Warning: this article may contain humor, sarcasm, parody, and perhaps even irony. Read at your own risk.
It now looks like the transformer failure was secondary. The sources are implicating a "hydraulic impact" This typically happens when a hydro unit is generating at full capacity, and the control valves, called wicket gates, close too fast. When that happens, the very large amount of water, with considerable inertia, that was headed for the turbine via pipes called penstocks now has nowhere to go. The lower portion of the penstocks, and the turbine case are then subjected to a very large over pressure and can fail catastrophically. The speed at which the wickett gates can close is typically set in the turbine governor and then checked and verified at least once. Unfortunately, this looks a lot like poor procedures, but one can never know for sure until the investigation is completed.
The power station converts gravitational potential energy to electrical energy at the rate of 6400 Megawatts. I have no idea how many transformers are involved, but in terms of the total, that's 6.4Giga Watts, or Joules/second. To put that in perspective, 1 tonne of TNT is 4.184 Giga Joules. If there is only one transformer for the dam and this transformer shorts, every second there is up to an equivalent energy of 1.5 tonnes of TNT being converted to heat in a very small space as opposed to providing useful power all over the electrical grid. If there are any ordnance experts here, I'm sure they can clue you in to what 1.5 tonnes of TNT will do. Actually, a bit of googling yields that there are 4 weights of general purpose bombs the US military uses. The largest is Mk84, at 908kg. The others are 113kg, 227 and 454kg.
To compound matters, what will happen is that the oil will turn into gas, but there is a metal shell that will prevent the oil from boiling over. The longer this metal shell is able to withstand the pressure, the bigger the explosion. Just multiply the 1.5 tonnes/second figure by the number of seconds the explosion is contained to get an idea of how powerful the explosion might be. If some of this oil can ignite, add more energy into the equation. However, it does not even have to ignite in order for there be damage equivalent to a bomb going off.
If I have seen further it is by stealing the Intellectual Property of giants.
OK replying to myself, bad form I know, but anyway, it looks like they had the transformers in a row along the back of the powerhouse. Which makes sense electrically I guess, step up to a higher voltage close to the generator. but in terms of what has happened, maybe not so good, if indeed the transformer did initiate the problem.
However, looking at the videos, one shows the event from the front of the plant, eg the downstream side, and there are first some sparks and then lots of water. We wouldn't be seeing the transformer from there, those flashes must be from the generator, and then the flooding water would come from the turbine as the whole thing takes itself apart. (It seems two of the generator sets destroyed themselves.) I will go out on a limb and say that this video shows a turbine generator set which was running when things went wrong, which argues against the transformer being under repair when it happened. Although there would be spares, I suppose they might have been working on one and whatever went wrong took out the live ones, initiating the whole thing. I say that it would be running since if the set was stopped, an explosion nearby could take out the penstock and cause a lot of water to flood, but going by the videos there was also electrical effects, more like you would expect if the generator set tried to take itself apart.
There is of course a scary amount of energy stored in the rotating parts, plus of course the available energy from the head of water in the dam. Normally the turbine would be controlled by the vanes around the rotor in the snail casing, but once an accident like this has happened they would have to drop the gates at the top of the penstocks.
Hey AC, check out New Here's posting history - Nothing but that same tired old joke in the last 20-odd posts.
It hasn't been funny for a lo-o-o-o-o-ng time. But it certainly was funny then.
Ahh - My eye!
The doctor said I'm not supposed to get Slashdot in it!
What was not reported but is shown in the videos is what happend when the transformer faulted and suddenly threw a short on a turbin. The torque on the generator tore it loose from the generator deck and the kinetic energy shreded the shell of the generator. The armature ripped the water turbine out as this mass flew about. This let the water into the generator deck and hydrostatic pressure blew out the generator deck wall. The transformer that shorted is outside. The light from the arc can be seen to the left of the rupture. The petcocks feeding the turbine deck were closed which shut down the fountain of water.
The water fountain is because the turbine core was ripped out by the disentigrating generator above it. This was not reported.
My father was a powerhouse operator on 2 of the hydro plant on the Columbia River Basin. As such, I have had the cooks tour of hydro operations.
The high voltage transformers to convert the generator output to the high tension line voltage are outside the powerhouse. A turbine deck in the powerhouse looks like this.
http://3.bp.blogspot.com/_7rnI15qf-JM/SE9LY0Qe_gI/AAAAAAAAGWw/IQ_c0S2khmY/s1600-h/DSCN3116.JPG
Now watch the videos again of the powerhouse damage. Several of the generators are simply shrededed and not present. The water turbine is pulled out of the deck on one. This is where the fountain of water entered the powerhouse. Note, there are no large transformers in the powerhouse.
The truth shall set you free!
Urrrrghhhh, my eyes! Back to high-school physics class 101. Seriously, how did this get modded +5?
The water applies a force on the turbine blades, so that the turbine keeps spinning. Remove the water flow, and the speed of the turbine will start decreasing immediately (due to friction). The spinning down phase may indeed take a while due to inertia, but without an external force (such as the water) applying pressure the speed of the turbine is going in only one direction, and that's down.
It seriously makes me wonder when something like this gets modded +5, on *slashdot*, where supposedly such knowledge is already above average level *shudder*.
Every expression is true, for a given value of 'true'