Blades certified before 2019 may be susceptible to damage from a destructive and anomalous type of lightning strike. Lightning protection systems (LPS) have been tested to an international standard since the early 2000s; however the focus was mainly on cloud-to-ground lightning and associated high energy levels. But there is another type of lightning that is less well-known. Difficult to detect and record, this elusive type of lightning can wreak havoc on wind turbine lightning protection systems.
This mysterious type of lightning is not normally seen, unless there is a really tall object nearby. Wind turbines are in that category; even 1 to 2 MW machines are relatively tall. Wind turbine designers are now pursuing 20 MW machines that will reach higher into the sky than ever before. Early estimates put 2 MW blade tips at over 300 m above the ground, taller than many buildings and even radio towers.
This creates a new level of lightning threat to wind turbines: the dreaded upward lightning.