  Power-grid systems constitute one of the most complex man-made spatially
extended structures. These operate with strict operational bounds to ensure
synchrony across the grid. This is particularly relevant for power-grid
frequency, which operates strictly at $50\,$Hz ($60\,$Hz). Nevertheless, small
fluctuations around the mean frequency are present at very short time scales
$<2$ seconds and can exhibit highly complex spatio-temporal behaviour. Here we
apply superstatistical data analysis techniques to measured frequency
fluctuations in the Nordic Grid. We study the increment statistics and extract
the relevant time scales and superstatistical distribution functions from the
data. We show that different synchronous recordings of power-grid frequency
have very distinct stochastic fluctuations with different types of
superstatistics at different spatial locations, and with transitions from one
superstatistics to another when the time lag of the increment statistics is
changed.
