Current and voltage measurement using optical crystal based devices

In recent years research and development work-involved with producing viable alternatives to conventional current and voltage measurement transformers has accelerated. This paper deals with optical crystal based devices utilising the Faraday magneto-optic effect and the Pockels electro-optic effect. These types of optical transducers have particular advantages at power system transmission voltage levels due to their passive nature and dielectric coupling to the conductor, and the authors believe they offer greater commercial potential for HV applications than other forms of transducer. The type of optical sensor that will be described and discussed in this paper is termed an unlinked sensor, implying the magneto-optic medium does not fully enclose the conductor and thus only `samples´ the magnetic field at a single point around the conductor, and-likewise the electro-optic sensor `samples´ the electric field at one point and does not integrate the measurement between conductor and earth. This arrangement makes for a compact, robust sensor head and ease of manufacturing