On 03/05/2013 07:10, harry wrote:
The grid frequency is controlled by the speedof the generators. The
only way to change that is change their speed. They are all linked
together no single generator can run faster than the others.
They are locked together as surely as they were all on the same shaft
by the alternating current they generate.

I think not. They can be a few degrees out of phase; those that lead are
putting power in, and those that trail are taking power out. I dare say
the pumped-storage systems do both at different times.

Andy