Fiber Optic Current Sensor Prototype for Low DC Measurements in the Power Grid

Our society is dependent on a continuous supply of electrical energy. Therefore, it is essential to closely monitor all occurring signals in the transmission grid to assess their effect on the grid's components and security of supply. In particular, the time course and distribution of direct currents such as geomagnetically induced currents is of great interest. In this paper, we report progress on the development of a fiber optic current sensor intended to observe direct currents on all three phases of a high-voltage power grid. The device exploiting the Faraday effect can be described in a theoretical model using Jones formalism. We calculated the sensor scale factor when using twisted single-mode and spun HiBi fiber as the sensing head, giving implications on the applicability of those fibers for a highly sensitive fiber optic current sensor. Laboratory results of the sensor prototype show a linear current relationship for currents below 1 A.