News Damn this day...(Suicide attack and power plant disaster)

[Artlav]

I don't speak Russian, was that guy laughing at it? I am guessing he didn't understand what he was witnessing?

The first one asked that maybe they should run away, the other one laughed.

 

[Urwumpe]

The first one asked that maybe they should run away, the other one laughed.

I am more impressed by the guy who ran towards the inferno, I am sure he saw the transformer shorten.

 

[Notebook]

Indeed, he probably knew what was happening, Brave chap.

N,

 

[SiberianTiger]

http://www.canadaeast.com/news/article/812523

Russia's top industrial safety oversight official said Saturday that negligence was a major factor in a devastating accident at the country's biggest hydroelectric power plant, and hinted that high-level officials could face trial over the disaster that killed 75 workers.

The chain of events that led to the accident began hundreds of miles (kilometres) away in Bratsk, where a fire at another hydropower facility caused damage that prompted authorities to increase the burden on the Sayano-Shushenskaya, Kutin said. One of its 10 turbine-generator units, which had been idle, was switched on to compensate and soon strained past its limit.

Part of an overstrained turbine unit weighing 1,500 tons snapped off its restraining bolts and sailed 14 metres (45 feet) into the air, he said, unleashing flooding, short circuits and wreckage that crippled the plant and doomed dozens of workers in seconds.

There is also information on some of the nuts that had been missing from the fixing studs of the cover #2.

This all still does not explain to me why overstraining was that fatal for the turbine.

A couple of picture links to add to this:

http://www.boston.com/bigpicture/2009/09/the_sayanoshushenskaya_dam_acc.html

http://englishrussia.com/?p=5141

 

[Urwumpe]

This all still does not explain to me why overstraining was that fatal for the turbine.

Think simpler - what does a turbine do? It converts a total pressure drop in the flow of water into energy.

Now, go one step further, what does it mean? If a turbine would be perfectly idle, it would not take energy away from the water. It is rotating at exactly the speed needed for keeping the water flow at it's total pressure. It would produce zero torque and there would be only small friction at the turbine surfaces.

The generator is the next element: The more electrical energy you demand, the more torque is required for turning the generator - the speed of the generator+turbine drops. That is why you notice increased power demands in power networks by the frequency of the AC current dropping.

Now, if you slow the turbine down faster than usual, by the generator requiring more torque, the turbine lags more behind the idle state, and more torque is produced by the turbine until the lag reaches a new equilibrium - the torque of turbine increases as long as energy in the water is available and at the same time, the pressure at the turbine blades increases. The more torque you demand from the turbine, the more you strain it by having higher pressures acting at the turbine instead of just flowing through the turbine unused. The increased lag (equivalent to the angle of attack on a wing) also increases the amount of cavitation at the turbine parts, eroding it quickly.

At the same time, the rotation forces inside the turbine increase as well, since a turbine is not free of mass and inertia.

Short: The more you demand from a turbine, the more likely is it that it breaks.