  Fluctuating wind energy makes a stable grid operation challenging. Due to the
direct contact with atmospheric turbulence, intermittent short-term variations
in the wind speed are converted to power fluctuations that cause transient
imbalances in the grid. We investigate the impact of wind energy feed-in on
short-term fluctuations in the frequency of the public power grid, which we
have measured in our local distribution grid. By conditioning on wind power
production data, provided by the ENTSO-E transparency platform, we demonstrate
that wind energy feed-in has a measurable effect on frequency increment
statistics for short time scales (< 1 sec) that are below the activation time
of frequency control. Our results are in accordance with previous numerical
studies of self-organized synchronization in power grids under intermittent
perturbation and rise new challenges for a stable operation of future power
grids fed by a high share of renewable generation.
