Lightning and Wind Turbines

Ars Technica:

To see what was going on, Joan Montanyà and Oscar van der Velde of the Universitat Politècnica de Catalunya in Barcelona and Earle Williams of MIT set up an array of radio sensors spaced kilometers apart around an area with several wind farms in Spain. The system maps the location of lightning radio emissions in three dimensions.
The array caught several interesting phenomena in the act. On a few occasions, periodic flashes about three seconds apart were detected over wind turbines—in one case lasting for over an hour. These turned out to be very low-energy discharges that sparked upward each time a blade of the turbine swept past the high point.
Most of us are familiar with cloud-to-cloud and cloud-to-ground lightning, but the sensors picked up a fairly extraordinary ground-to-cloud-to-ground strike during one storm. For most cloud-to-ground strikes of tall objects, fingers of positive charge called “leaders” often travel upward from the object before reaching a region of negative charge in a cloud. Current then courses downward through the path of that leader, through the object being struck, and into the ground.
In this case, a negative leader reached upward from the turbine and into an area of positive charge about 5 kilometers up. This is the kind of strike that can damage turbines so badly. In this case, however, there were both positive and negative charges interacting in the clouds, and the downward strike lashed out laterally, striking the ground fully 20 to 25 kilometers from the turbine.
The researchers also captured some high-speed footage of lightning striking some nearby wind turbines, seen below. Of interest here is the fact that several turbines get involved in a single strike. Positive upward leaders jump from three different turbines at the same time, with one becoming the lucky recipient of the downward strike. Close examination also shows small, failed leaders extending from the tips of three other turbines. This shows that the turbines weren’t very well isolated from each other electrically.

That is kickass.