Geomagnetically induced currents modelling and monitoring transformer neutral currents in Austria

Transmission system operators are responsible for security and reliability of their grid. An important topic is the analysis of possible risks for the transmission system network. The paper presents actual results about geomagnetically induced currents (GIC) in the Austrian transmission system. Because of problems with unexpected noise at some transformers, investigations were started, which gave an indication that DC could be the source of this noise. Due to the particular geological structure of the country, the influence of GIC in Austria is higher than for the most other countries in Central Europe. A simulation model to compute GIC was set up and compared to the measured DC transformer neutral current. The comparison of the simulated and measured currents shows a good correlation. High geomagnetic disturbances, which lead to high currents according the simulation model, can be confirmed by the measurement. Differences between measurement and simulation can be seen in the region of “fast” fluctuation within seconds. By detailed analysis of the times of occurrence it was shown, that currents from underground railway, which are operating with DC, flow through the transmission grid, too.