Slashdot Mirror
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?
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.
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
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.