Vattenfall, the Swedish wind farm owner/operator, has completed its investigation into the collapse of a turbine at the Eemmeerdijk wind farm near Zeewolde in January. The company has determined that the cause of the collapse was a “loosely vibrated pitch cylinder.”
The incident was attributed to a defective component in the blade position control system of the turbine. This system allows the blades to be turned “out of the wind,” effectively stopping the turbine. On January 4th, strong winds caused the operating system to malfunction, preventing the blades from being adjusted to a different position and resulting in excessive wind exposure.
Controlling the position of the blades is crucial for slowing down a turbine. However, turbines also have a mechanical brake. Although the brake was activated, it failed to stop the turbine. Consequently, the generators supplied twice the intended electricity, leading to their failure. The blades began spinning at an increasingly faster rate until one of them broke off. The imbalance caused the upper part of the turbine to break off as well.
It is noteworthy that the Eemmeerdijk Wind Farm is the only wind farm in the Netherlands where Vattenfall has employed this particular type of two-blade turbine. Most wind farms utilize turbines with three blades, each equipped with its own control system. In the event of a control system failure in one blade, the other two blades are capable of bringing the turbine to a halt, thereby preventing similar incidents.
The turbines at Eemmeerdijk were already scheduled for demolition later this year and will not be operational until then. Following the accident, all 16 remaining turbines at the wind farm were promptly shut down.
