Improved Calibration Method of the Photonic Current Sensor for Monitoring HVDC Networks

This letter presents an improved calibration method for a novel optical current sensor (OCS) based on the integration of photonic and piezoelectric technologies to facilitate the distributed measurement of current within high-voltage direct current (HVDC) networks. The sensor is designed to fit in an HVDC subsea cable splice to provide remote distributed current measurement for enhanced monitoring and protection of HVDC power cable assets. The prototype transducer comprises a nonlinear amplifier with an enhanced dynamic range to reduce the measurement errors that are dominated by the limitations of the sensor interrogation system at low input signal levels. The improved calibration method incorporates segregated piecewise curve fitting into the sensor calibration characteristic. The experimental results demonstrate the significant reduction of the measurement errors showing the potential of the sensor to comply with the accuracy requirements set by the IEC 61869-14 standard for Class 1 direct current transformer (DCCT) devices.