[McMurdo]

I saw that documentary, if it was the same one, from the national grid control centre. Lots of LCD monitors and guys in shirt & tie scanning the tv schedules and keeping an eye on the big LED frequency meter. At one point the chappie told the reporter he'd have to 'bring another power station online soon' as the frequency was getting too low; apparently the drop was a good indicator of more power needed.

I assume power generation works in a similar way to other supply & demand systems (such as compressed air) where there's a hardcore of bulk supply for coarse adjustments and then a smaller, more easily variable set of generators that take up the slack to fine tune everything up or down.