Following the collapse of a turbine at the Eemmeerdijk wind farm near Zeewolde in January, Vattenfall has wrapped up its investigation into the cause.
The Swedish wind farm owner/operator has attributed the cause to a “loosely vibrated pitch cylinder”.
The incident with the wind turbine was caused by a defective component in the system that controls the position of the blades of a turbine, which is able to turn the blades “out of the wind”, so that the turbine can be stopped.
Vattenfall stated: “On 4 January, the wind picked up strongly and that operating system stopped working.
“As a result, the blades could no longer be set to a different position and caught too much wind.”
Control of the blades is the most important way to slow down a turbine.
However, turbines also have a mechanical brake.
That brake was activated, but was no longer able to stop the turbine.
As a result, the generators supplied twice as much electricity as they were designed for and failed. The blades started spinning faster and faster, until finally one broke off.
After that, the turbine became so unbalanced that the upper part of it also broke off.
Eemmeerdijk Wind Farm is the only wind farm in the Netherlands where Vattenfall has used this type of two-blade turbine.
Most wind farms feature turbines with three blades, and each blade has its own control system.
If one of the control systems of one blade fails, the other two blades bring the turbine to a standstill and prevent an incident like this.
The turbines at Eemmeerdijk were already planned to be demolished later this year.
They will no longer be in use before that time.
Immediately after the accident, the other 16 turbines of the wind farm were shut down.