While studying the technical, financial, and operational aspects of a pump storage hydro plant, I came across to the Dinorwig power station which was mentioned in the text book that I was reading. Dinorwig power station is a 1728 MW pumped storage hydroelectric plant in the North wales. Aside from its incredibly large capacity, what is more interesting about this plant was its very fast ramp rate. That is, with all six units synchronized and spinning-in-air, it can achieve a 0MW - 1800 MW load in approximately 16 seconds. That is very fast that it is capable of rescuing a power system that is about to collapse due to isolation of other generating units. In short it is a very good back-up as well as a frequency and load following reserve.

Other operational parameters of Dinorwig power station:
Generator/Turbine: six 288MW GEC generator/motors coupled to francis-type reversible turbines
Rotational Sped: 500 rpm
Blackstart Capability: OK
Turnaround efficiency: between 70 and 80% efficiency - i.e. it uses 20% more electricity (when pumping the water back up to the Machlyn Mawr) than it actually produces

Additional References:
http://en.wikipedia.org/wiki/Dinorwig_Power_Station