This brief document provides a case study of a wind energy facility in Texas and the effect of lightning strikes on wind turbine blades. Despite the 1.5 MW turbine blades having been equipped with lightning protection, the blades failed as a result of lightning strikes.
According to the report:
Lightning protection consists of several exterior copper “receptor” air termination discs, which are fastened to interior aluminum conductors running the length of the blade. Conductors are fastened to the blade and to one another with steel bolts. Near the blade root a portion of the conductor is imbedded into the fibreglas. The conductor transitions from the blade root area via bonding to the hub and thence to a ground reference.
Other components of the lightning protection systems were examined briefly.
The manufacturer provided satisfactory surge protection for sensitive electronics. Grounding requirements were completed “per manufacturer’s specifications” by the installation contractor.
The lightning conductor did not conduct as designed. Lightning created an internal shock wave from air or moisture expansion, or both. Lightning temperatures may have caused interior moisture to transition to an expansive state (steam). In turn, over-pressures stressed the blade to subsequent failure. Further research into wind turbine blade interior air/moisture expansion issues is needed.
Editor's note: The full report can be accessed by clicking on the .pdf link below.