Extreme space weather events can have severe effects on satellites and other technology in orbit, but also pose risks to ground-based infrastructure like high voltage (HV) transformers, railways and gas pipelines through the induction of geomagnetically induced currents (GICs). Modelling GICs requires knowledge about the source magnetic field and the electrical conductivity structure of the Earth to calculate the electric fields generated during enhanced geomagnetic activity.
The electric field in combination with detailed information about an electrical network’s topology and resistance parameters enable the derivation of GICs flowing in HV power lines. Directly monitoring of GICs at the ground neutral in substations is possible using a Hall probe, but scarcely implemented. Therefore, we have used the differential magnetometer method (DMM) to measure GICs at six sites in the UK power grid. The setup of the DMM includes the installation of two fluxgate magnetometers, one directly under a HV power line (400 kV) affected by GICs, and one as a remote site further away a few hundred metres away. The difference in the recorded magnetic field between the instruments allows for the inference of GICs in the line, via the Biot-Savart law, during geomagnetically enhanced periods.
Data from several storm events during 2018 and 2019 are presented. These show a good match to Hall probe measurements available from one transformer site in Scotland. Comparing the measured GIC at the DMM sites to the computed ones will allow us to validate the UK model, and to monitor GICs in real-time.