AN OPTICAL CURRENT TRANSDUCER FOR RESIDUAL CURRENT SENSING IN THE MILLIAMPERE RANGE

Current-sensing devices play an important role in electrical safety en gineering. Optical current transducers developed so far have been appl ied to the measurement of hundreds of amperes. This paper presents the design considerations for a magneto-optic sensor suitable for use in a residual current device (RCD) where the requirement is to measure di fferential currents in the milliampere range. The principles of operat ion, electronic design and experimental results for such a device are presented in this paper. In high-power electrical networks, electrical isolation, saturation and frequency-response characteristics of the m agneto-optic sensors can provide a cost-effective and versatile sensin g method. Results show that the device has an independent linearity of 99.91% and a sensitivity of 40 mV A(-1). (C) 1998 Elsevier Science S. A. All rights reserved.