Development And Testing Of Optically-Interrogated Current Sensors

We report on the design and construction of a lowcost, accurate optically-interrogated low voltage transducer (LVT) which, when combined with a Rogowski coil or conventional current transformer, forms an optically-interrogated current sensor (OCS). The LVT has been designed to be capable of being mass produced. The OCS requires no power supply and is interrogated remotely. Furthermore, it can be multiplexed in series or in parallel, allowing for multiple current measurements at different sites to be made by the same interrogator. The LVT and OCS have been tested against the accuracy requirements of the IEC 60044-8 standards for electronic current transformers (ECTs) both by direct signal injection, and by primary current injection when interfaced with a conventional PX class CT. The LVT and OCS are shown to meet the stringent 5P protection class requirements and also the additional requirements of the Transient Protection Electronic (TPE) class.