On Mon, 31 Aug 2009 17:15:50 -0500, Ignoramus25738
wrote:

On 2009-08-31, Cydrome Leader wrote:
damn shame. terrible tragedy.

the wiki article said the one turbine blowing up caused a electric shutdown
which resulted in the other turbines that were on line to overspeed and blow
up too.
amazing.

clever design.

An interesting story, all in all. Allows for good after the fact
thinking.

How would one stop a hydroturbine, if its electric load disappeared?
I would suppose that it would overspeed in seconds, so anything to
stop a turbine, would need to be done quickly and automatically.

Open some sort of a sluice in the line that feeds turbine with water,
to divert and dump the water elsewhere, would seem like the only
possible solution.

The amount of available options would depend on how quickly the water
would overspeed the turbine. Such a calculation should be possible
based on available data, such as water column height, turbine mass,
and turbine radius.

i

I read a long time ago (so take it for what it's worth) that to stop a
water turbine quickly, the best approach was a deflector. The water
is diverted from the turbine wheel by a blade until the penstock
valving can be closed. If you were to slam the penstock valve closed
too fast, the pressure surge from the dynamic head of a huge column of
water moving at speed would destroy the penstock, turbine, etc. I
think the reference was a Perry's handbook, but this was decades ago.

Hmm. Kind of sounds like what happened.

Pete Keillor