This is interesting, as this is clearly not the case in Carland, Delabole or Chivvy cross wind farms.
When they are under power, they appear to be spinning at "the same rate" whereas when they are being driven by the wind, the rates of spin vary hugely. In my estimation, they appear to be turning at different rates, which would suggest there is some sort of inverter at work, unless they are playing hell with the national grid!
My engineer chum explained why they turned them at a given rate (due to motor heating) as they are probably not driven through the same inverter.
What is curious is that when they are clearly being spun by the grid, rather than the wind, the blades are not feathered.
This causes me to believe my "it's all surfers" conspiracy javascript:emoticon(':lol:'):lol: