bridage refers in general terms to limiting the speed of something, as BD Finch has suggested.

However, in wind-turbine technology, it refers, by extension, to the method used to limit the speed, in situations such as that described in the ST.

This method is called "feathering" (mise en drapeau in the French aeronautic industry).

feathering involves "de-optimising" the pitch of the blades, so that they will not naturally turn at as high a speed as they would when set for full speed/operating efficiency/power-output.

It’s done this way because other methods would require mechanical or electrodynamic braking systems which wear out and/or generate un-wanted heat. The better solution is to avoid going over-speed from the outset by taking less energy from the wind.

In this case, it is not a question of reducing or limiting the speed as all windmills turn at the same speed (which determines the frequency of the power produced - 50Hz in Europe).

By altering the blade configuration, you can alter the amount of power produced and, as a by-product, the amount of noise generated. But, in ALL cases, the windmill will continue to turn at the same speed.

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Note added at 1 day1 hr (2017-02-26 19:08:51 GMT)
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Strictly speaking, different models of windmill can turn at different speeds but all of the same model turn at the same speed. As B D Finch points out, there is a gearbox that converts the relatively low speed of the blades to the higher speed required by the generator. However, this gearbox has a fixed ratio and the generator MUST turn at a fixed speed of 3000 (50 Hz x 60 seconds) RPM. This implies that the blade speed must be fixed as well. It does not necessarily have to be the same for two different windmills as they could have different gearbox ratios but, whatever it is, it has to be fixed.

You can verify this by looking at a group of windmills and noting that a blade reaches the highest point (i.e. straight up) at the same time on all of them even though they can be in different wind conditions.


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Note added at 1 day2 hrs (2017-02-26 20:17:33 GMT)
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Well, apparently there *are* variable-speed wind turbines but they are not very common. And they still have fixed-ratio gearboxes! Some of them are used for stand-alone systems where the frequency produced is (relatively) unimportant. The others have to convert their variable-frequency output to DC and back to AC at the correct frequency. This is an inefficient process and the losses incurred generally overwhelm the increased efficiency of the variable speed turbine. It also introduces nasty harmonics into the power grid.

I would strongly doubt that anybody here has ever seen one in operation.

For the purposes of this question, I maintain that wind turbines are fixed-speed.