Detection of geomagnetically induced currents on single phases in power grids using a fiber optic current sensor system

Abstract. Power transformers are an integral part of our electric power system. Parasitic direct currents in the alternating-current grid cause inefficient transformer operation and demand mitigation measures to protect the grid’s constituents. In particular, geomagnetically induced currents (GICs) arising from solar activity prove to be an unpredictable risk for grid operators. Within this paper, we present an interferometric fiber-optic current sensor system designed for long-term monitoring of GICs, allowing fully remote sensor control and data access. The developed sensor possesses a noise-limited threshold sensitivity of 2.64 mA Hz-1. We successfully demonstrate the first optical measurement of GICs on a single phase of the power grid during two distinct geomagnetic events, on both the low-voltage and the high-voltage sides.