Nova wrote:
krw wrote:

The water going through turbines is hardly pure. I doubt water
touches the generator windings themselves.

I've toured the Robert Moses power generation station in Niagara Falls a
number of times. The turbines are at the bottom of the dam to take
advantage of the water's pressure. The generators are on the top floor
of the structure to facilitate installation/replacement. The two are
connected by a massive shafts. You're correct, the water (hopefully)
doen't come near the generators.

Actually, large-capacity turbine-generators are typically H cooled to
enhance conductivity. One does not smoke in the vicinity...

http://www.gepower.com/prod_serv/products/generators/en/hydrogen_cool.htm

--