  Eruptive events on the Sun have an impact on the immediate surroundings of
the Earth. Through induction of electric currents, they also affect Earth-bound
structures such as the electric power transmission networks. Inspired by recent
studies we investigate the correlation between the disturbances recorded in 12
years in the maintenance logs of the Czech electric-power distributors with the
geomagnetic activity represented by the K index. We find that in case of the
datasets recording the disturbances on power lines at the high and very high
voltage levels and disturbances on electrical substations, there is a
statistically significant increase of anomaly rates in the periods of tens of
days around maxima of geomagnetic activity compared to the adjacent minima of
activity. There are hints that the disturbances are more pronounced shortly
after the maxima than shortly before the maxima of activity. Our results
provide indirect evidence that the geomagnetically induced currents may affect
the occurrence rate of anomalies registered on power-grid equipment even in the
mid-latitude country in the middle of Europe. A follow-up study that includes
the modelling of geomagnetically induced currents is needed to confirm our
findings.
