A prototype clamp-on magneto-optical current transducer for power system metering and relaying

A new type of Faraday effect based magneto-optical current transducer (MOCT) has been developed. This paper presents the theoretical background, engineering design, and test results of this clamp-on MOCT. The sensor consists of two separate clamp-on parts. This design avoids the need to break the current carrying circuit in order to have the conductor enclosed by the optical path. A feedback scheme has been designed to stabilize the light source. The MOCT has two output stages, 1 kA and 20 kA, so that it can provide current signals for both power system metering and relaying devices, The theoretical background of maintaining the light travelling through the glass prism to be linearly polarized and the analysis on the effects of dielectric and metal reflections on the linearly polarized light is presented in the appendix