A new current measurements system using an azimuth angle modulation method

With advancing opto-electronic techniques, current sensors which consist of a Faraday crystal have attracted much interest in measuring currents which flow at high potentials, such as UHV (ultra-high-voltage) transmission lines, because the Faraday crystal is a kind of insulator having an optical transparency for laser beams. When the current sensor is connected to a long fiber cable, it is very hard to accurately hold current information due to birefringence in the optical fiber, even if the polarized plane is preserved in the cable. From this point of view, the authors have developed a new current measuring system using an azimuth angle modulation method. From a series of experiments, it is found that the present current measuring system is useful for precisely and accurately measuring not only AC, but also DC current flowing at high potentials