Transient fiber optical current sensing during high-voltage short-circuit events

The aim of this work is to demonstrate the use of Fiber Optical Current Sensors (FOCS) for high frequency measurement of electrical currents at high-voltage level in the field. A non modulated Sagnac interferometer utilizing the Faraday effect is built and tested. In contrast to modulated systems, there are no hard limits regarding the signal evaluation to the bandwidth due to the measurement principle. The first functional test was successfully carried out in the laboratory. Current events with a bandwidth of ≈ 100 kHz were recorded in the field. Although there were problems with the stability of the operating point it was determined that an optical system is suitable for the high-frequency recording of electrical currents. A reference measurement with a conventional induction current probe was not able to record these high frequent events. Further measurements, which could result from the evaluation of the possible stability improvement through another measuring head, should be investigated.