  Feed-in fluctuations induced by renewables are one of the key challenges to
the stability and quality of electrical power grids. In particular short-term
fluctuations disturb the system on a time scale, on which load balancing does
not operate yet and the system is intrinsically governed by self-organized
synchronization. Wind and solar power are known to be strongly non-Gaussian
with intermittent increment statistics in these time scales. We investigate the
impact of short-term wind fluctuations on the basis of a Kuramoto-like power
grid model considering stability in terms of desynchronization and frequency
and voltage quality aspects. We compare intermittent feed-in with a realistic
power spectrum, correlated Gaussian noise of the same spectrum, and Gaussian
white noise. We found out that the likelihood of severe outages is mainly
determined by the temporal correlation of the feed-in. The intermittent nature
of wind power is transferred into frequency and voltage fluctuations. This
establishes a novel type of fluctuations with severe consequences on frequency
and voltage quality, which are beyond engineering status of knowledge.
