A New Coating for Reducing Wind Turbine Blade Lightning Damage

A novel wind turbine blade coating has been developed that
reduces lightning damage to the blades. It enhances the
effectiveness of existing lightning protection systems
comprised of a down conductor and one or more surface
mounted lightning receptors. It can be applied as a retrofit to
existing turbines or applied to new blades. The coating
contains small discrete conductive elements that locally
enhance the electric field in the air above the elements to
promote the early formation of a surface flashover. This helps
leaders emanating from the existing receptors travel faster and
farther over the blade surface to connect with the downward
stepped leader from the clouds before competing streamers
that originate from the blade’s interior have a chance to
puncture through the skin and cause damage. A key feature of
the coating is that it is does not provide a conductive pathway
for the strike. Rather, it enables a conductive channel of
ionized air adjacent to and above the surface. This non-
sacrificial operation allows the coating to remain effective and
undamaged even after multiple strikes.

The coating was empirically developed over the past three
years using extensive small-scale and large-scale high voltage
and high current testing. The first phase consisted of testing
flashovers across small samples up to 100 mm in length with
voltages up to 70 kV. Subsequent optimization used 610 mm
square panels combined with a 2-meter air gap in a high
voltage lab capable of reaching 2.4 MV. The material, size,
shape, and concentration of the elements in the coating were
carefully optimized to a narrow range of parameters found to
be most effective. For the final formulation, the metric of
average flashover time was reduced, on average, by 76%
compared to a baseline topcoat. The coating’s mechanical
performance was also tested to ensure the improved lightning
protection does not come at the expense of the other functions
a topcoat is designed to perform. Photos demonstrate the
desired increase in streamer and leader activity around the
lightning receptor with the coating. Excellent damage
resistance was verified with full-scale currents up to 200 kA.
Finally, the coating was validated with IEC standard initial
leader attachment tests on GE 1.5sle wind turbine blade tips 5
meters in length. Results showed a significant increase in the
level of protection with the coating properly applied compared
to a blade without the coating. If applied to operational
turbines, a 73% reduction in punctures was estimated. Field

tests are scheduled on multiple turbines at two operational
wind farms beginning in the summer of 2022.