Pollution
Humain
Environnement
Economique

At around 10:00 p.m., alarms sounded on the operating system of a wind farm. One of wind turbine had been shut down and the rotational speeds of the rotor shaft and the electricity generator were out of sync. Upon arriving at the wind farm the following morning, the operator saw that the last seven metres of a 44-metre blade had broken off and that several fragments had been thrown as far as 150 m from the 78-m-high tower. The operator placed the four other turbines in the park in a safe condition and began investigating what happened. He picked up the debris and secured access to the farm.

Ruling out the possibility of lightning or strong gusts of wind, he thought that a defect in the blade’s leading edge may have been the cause. The damaged blade was replaced. The wind turbine was put back in service 8 months later.

The manufacturer’s investigation determined that a manufacturing defect was the cause. While excess adhesive was being sanded after the blade had been released from the mould, the layers of fabric on the blade’s leading edge were mistakenly cut by hand along the joint between the two shells. As a result, the shells were held together only by sealant and finishing paint.

The four other turbines in the park were inspected. Two were subsequently returned to service while defects were found on the other two.

  • the bonding planes between the internal structural beam (spar) and the aerodynamic half-shells (blade shells) had significantly come apart in spots;
  • cracks affecting the structures of the aerodynamic shells and bonding planes of the leading and trailing edges of the blades were found;
  • diverter strips, located at the tips of some blades, were either missing or damaged.

The operator undertook to make the necessary repairs before the restarting these two wind turbines.