<title>Optical current transducer for electric power system</title>

Abstract

The expansion of the high voltage power transmission system since the 50s and 60s has aroused an interest in using optical techniques for measuring the electric current. As the most promising method among them, a current measuring method which uses a magneto-optic effect called the Faraday effect have been proposed. In principle, this method is excellent in such aspects as control of electromagnetic induction noise, rationalization of electrical insulation, extension of dynamic ranges and frequency bands. The authors have developed an optical current transducer based on the Faraday effect of dense flint glass for the purpose of utilization in 110 KV substation. It uses the rotation of the plane of polarization by a magnetic field exhibited in certain glasses. As a result of the development, high accurate optical current transduce such as the ratio error +/- 0.2% when compared to the reference CT and temperature stability (from -20 degree(s)C approximately +40 degree(s)C) +/- 0.5% were obtained. Furthermore, short-circuit current (11 KApeak) was measured with the optical current transducer, and the accuracy was +/- 3%, the bandwidth was approximately 2.5 KHz. This paper describes the principles, structures, operations, and testing results of the optical current transducer.