An optical current transducer having linearity better than 0.4% from 4 to 108,000 A

NxtPhase has been working on a fiber optic protection level current transformer (CT) that exceeds the IEC standard 60044-8 and rivals the most stringent standards. One of the major practical problems facing the manufacturer of a current sensor rated in the 100 kA range is the cost and complexity of testing the sensors. A number of laboratories around the world have test capabilities at these levels, but the time and expense of testing each sensor to these levels is prohibitive. Fiber-optic current sensors, because they are inherently linear devices, can be effectively calibrated at these high current levels by setting the scaling with much lower currents (say 4 kA) and then using the linearity of the sensor to give an accurate result at high peak currents.