Digital Optical CT Application to HVDC Earthing Line Fault Measurements

A digital optical current transducer designed for the measurement of small alternating currents is applied to current measurements for an HVDC earthing line. A novel scanning band pass filter was used to make experimental measurements of small high frequency currents. Currents from 1 kHz to 5 kHz and 0.2 A to 2 A in the presence of 20 A
_DC
have been experimentally made. With accuracies of less than 0.4% for the 2 A measurement. The optical current transducers can measure currents remotely up to 20 km from the converter station. This new optical current sensor measurement method can allow the location of faults on HVDC earthing lines.