Analysis of the impact of geomagnetic disturbances on the Austrian transmission grid

Transmission system operators are responsible for secure and reliable operation of their grids. An important topic is the analysis of possible risks for the transmission system network and the system equipment. Triggered by unexpected audible noise at some HV transformers, investigations into the possible cause were started. These indicated that DC are responsible for the increased noise emission. First measurements in a substation of the Austrian power grid revealed the expected DC components in the transformer neutral current for the first time in Austria. Generally it is quite challenging to monitor rather low DC in the presence of high AC. Further research revealed that geomagnetically induced currents are likely the source of this disturbance. These low frequency currents are well-known in areas close to the magnetic poles, but not for Central Europe. Different model can be used to calculate the geomagnetically induced currents. A simulation model for the Austrian high voltage power grid was developed and tested using the planewave method and a 1D-layered earth conductivity model. The outcomes of the simulations are compared with the measurements and the results are presented.