Faraday effect optical current sensor

Abstract

Optical current sensors based on the Faraday magnetooptic effect are able to meet the technical demands for the large current measurement in the power industry. Based on the classical electromagnetic theories, the Faraday magnetooptic effect is analyzed, and the conclusion that the Faraday effect in the diamagnetic media is independent of temperature is obtained. Thus, a type of diamagnetic media, SF6 glass, is selected as the sensing element in the optical current sensor. Since the rotation of the azimuth of polarization is equivalent to the evaluation of Ampere's law for a closed path around a current carrying conductor, particular attention is paid to designing and fabricating a closed path optical current sensor. In this study, the geometric compensation method is adopted and, a closed loop and an openable optical current sensors with frame structure are designed and fabricated. With the closed loop optical current sensor the experimental investigation on AC/DC current sensing and frequency response have been carried out. The exper­imental studies on the stability and repeatability of the openable optical current sensor with and without the index matching fluid between the optical contact sur­faces have also been carried out. According to the experimental results the proof of concept closed loop and openable optical current sensors are successful.