[classicman]

Or it could be this ...

Chain of events

• Vestas state that service was requested for the turbine, following a malfunction of the brakes (cause: worn brake). At the last routine major checkup it was noticed that the main gear made some noise. It was then recommended to have an endoscopic inspection done and a price quote was forwarded.

• A service team from Vestas arrive Friday morning to check the brakes. The brakes were repaired and checked.

• The braking mechanism is tested eight to ten times from the nacelle [engine house on top of the tower]. Then the turbine is restarted from the bottom of the tower with the intent of putting it back into normal production. At this point, the wind is very strong. The airbrakes at the tip of the blades are used to control the speed of the rotor, prior to attaining operational speed, according to Vestas. That means the tips of the blades are turned out during the start.

• During the start of the turbine, just when it is put back on the grid, noise is heard from the nacelle. The service personnel press the stop button. The turbine’s control system starts a controlled shutdown procedure, but a large crash is then heard (probably the gear that fails). The turbine is shaking strongly and cable assemblies, etc., fall down inside the tower. The rotor stops abruptly for a moment, but then starts turning again. The speed of the rotor is rather low, but it is noted that the turbine no longer can be controlled from the control panel and stopped by the brake on the high-speed axle. The personnel evacuates the tower immediately. Outside, it is observed that the airbrakes at the tip of the blades have broken off.

• The wind is very strong. The turbine continues to gain speed, and attains speed beyond its design limit.

• The service personnel contacts the local police and assist in establishing a safety zone of 400 meters (1300 feet) and warn the neighbors. This continues for 21/2 hours.

• The turbine wrecks. The events are filmed by a neighbor and later shown on the TV2 station. The result is that the blades collapse, the tower is hit and is strongly indented. The nacelle is bent forwards (against wind direction). Pieces of all three blades are thrown a great distance downwind from the tower, almost 180 degrees.

• The nacelle and the upper part of the tower falls to the ground in front of the tower. The generator falls out and rests next to it.

• Large pieces of the blades land 200–300 meters (600–900 ft) away, while small pieces appear to have flown 500 meters (1600 ft). Smaller, lighter pieces are found near a farmhouse, about 700 meters (2200 ft) away, though these may have landed and then been blown further by the wind, as the wind was very strong.

• The lower part of the tower remains standing. An inspection of the gear shows it to be damaged.

• Nobody was hurt.

Link

ETA - Bruce was right , again.