| In this dissertation, the use of bulk Yttrium Iron Garnet crystals with large magneto-optical effect and fast response as optical sensors for the measurement of small transient currents is discussed. The sensor is compact and robust, while advantages such as high intrinsic sensitivity, fast response and also intrinsic electrical isolation are offered as well, which make it attractive for measurement of small transient currents in high voltage power systems.After a brief introduction, in which the motivation of the project is presented and several general considerations of sensor design are discussed, various state-of-the-art current sensors are reviewed and compared. A comparison of various properties of different magneto-optical crystals is also presented in this thesis, after which the original research work is summarized.The basic principle and also tips on the design of the sensor are presented. The various sensor characteristics are demonstrated, which shows good linearity and fast responsivity. A four-sensor system for investigating the conductor position dependence is described and measurement results have shown good consistency with the theoretical calculation.At last, a configuration optimized for measurement of small transient currents is designed. The performance of this configuration is experimentally characterized, and the capability to measure transient current down to 20mA is demonstrated. |
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