Wind turbine performance with wind speed generally looks something like the diagrams show below. Ratio your turbine's rated power to the maximum values you see in the curves below. Different blade and generator characteristics can be tuned within reason to give peak performance at a specific constant wind speed, which shifts the peaks seen below to the left or right accordingly. The key to yearly output of wind turbines is to buy, or design a wind turbine that has characteristics giving maximum performance at your average yearly wind speed. An average power output factor for a year calculated for many different types of turbines over a large territory, show that the combined output for the year will be 12-18% of all the turbine's average power rating. That average power output factor is assuming that the turbines are simply available for the whole year (not down for maintenance) so actually it means whether the wind is blowing or not at any given time. i.e. A one(1) kW turbine will produce, with a 12% average power output factor, 1 kW x 8760 hrs/year x 0.12 = 1051 kWh, which at perhaps a high value of 20 cents/kWh, will produce electricity valued at $210.24 over the next year. If you could get that average production factor from 12% up to 18%, which may be possible in a "good wind location" , the electricity produced during the year would be worth $315
A good wind location means NOT that the wind blows fast every day or night, but how close to the design wind speed the wind blows for the whole year. If you have high wind velocities, design your turbines for that higher average velocity and you will get more power. Anyway... have a look,
Several different power curves for different models as shown,
Tripping all wind turbines at a wind speed of 25.5 m/s is the unfortunate turbine characteristic that causes the electrical distribution system to become unstable during wind storms. There were 2 major system instabilities in ERCOT ( texas ISO) 1 year apart , in Feb 2007 + feb 2008, in which over 1 GWe of power was lost from the grid over a 35 minute period as the wind speed exceed 25.5 m/s at a large wind farm. Major industrial consumers of power were ordered to shut down and there was a dramatic effort to restart idle gas turbines to make up the difference. Larger instabilities to the grid occurred when the wind speed later dropped below 25.5 m/s and the wind turinbes re-loaded.
One result is that wind farms are now required to provide wind speed data to the ISO in real time, so the ISO can predict when such an instability will occur and can get at least a 30 minute lead on restarting gas turbines.
"Whom the gods would destroy, they first make mad "
Would make more sense to me (from an operational standpoint) if they had staggered trip points to prevent the hard cut-off of an entire farm from the grid at the same time.
There is an excellent primer on the mechanical and structural limitations of large wind turbines in the Sept 2013 issue of Mechanical Engineering, by J. Aho et al, titled "Controlling Wind Energy", and the effects of those limits on system stability.
"Whom the gods would destroy, they first make mad "
I believe the answers given so far may have not completely answered the original question.
Cannotfly, you are welcome to post a reply of your own, to let us know if your curiosity has been satisfied.
It's possible that the OP is asking about the mechanical performance of a rotor when operated above or below its optimal tip-speed ratio, with no electrical conversion in the equation. It's also possible that the OP wants to know about blade pitch controls. Just letting the OP know that the door is open to further questions, because it may not be obvious to all new members.
No, it is based on some specific design quantity or yield point - minus a (small) margin.
Regardless, if every turbine in a wind farm is going to be the same (same rating, same manufacturer, same size blades and same materials and same parts) which is the only reasonable way to buy many and build many in the same place, then you HAVE to expect them all to trip out at exactly the same point during the rising winds of a storm front. At least the power-on points are a little more gradual, since some power is produced by every turbine as they speed up, even at below-rated speeds.
If every fifth turbine were different from every fourth were different from every third turbine, then you'd have fewer chances that all would trip off at the same time (only 20% would drop off in the same wind speed), but ... You'd never keep it maintained.
