A New Data Set of Line GICs measured with the Differential Magnetometer Method in the UK High Voltage Power Grid for the Years 2018-2020

Extreme space weather events can have severe effects on ground-based infrastructure including power lines, railways and gas pipelines through the subsurface induction of geomagnetically induced currents (GICs) generally, though not exclusively, affecting mid-to-higher latitude countries. Modelling GICs requires knowledge about the source magnetic field and the electrical conductivity structure of the Earth to calculate the induced geoelectric field during enhanced geomagnetic activity. The geoelectric field in combination with detailed information about the network topology enables the derivation of GICs in power lines. Directly monitoring GICs in power grid substations is possible, for example with a Hall effect probe, but this is uncommon in the UK. Therefore, we used the differential magnetometer method (DMM) to measure GICs indirectly at twelve sites in the UK power grid. The setup of the DMM includes the installation of two fluxgate magnetometers, one directly under a high-voltage power line affected by GICs, and another at a remote site further away (typically >100 m). During geomagnetically enhanced periods, the difference in the measured magnetic field between instruments allows for the calculation of GICs in the local power line segment via the Biot-Savart law.

We collected data from multiple locations across the UK power grid in the years 2018-2020, monitoring regions that were modelled to experience high GICs. Though deployed during the recent solar minimum with few periods of greater geomagnetic activity, we recorded several minor geomagnetic storms, which we report here. This data set provides a basis to refine and validate our computational model of GICs in the UK power network.