Field Experiment and Modelling of DC Electronic Current Transformer with Digital Output

The DC electronic current transformer (DCECT) is the main data source of the control and protective system of a HVDC transmission system. However, the research on transient modeling of DCECT for electromagnetic simulation is primarily focused on the primary side, lacking research on the modeling of the secondary side. Due to the positioning of DCECT deep inside the substations, it is challenging to conduct large-scale field experiments. The modeling problem of the secondary side of DCECT remains unresolved, which poses significant challenges for the simulation of various field experiments involving DCECT. In order to modelling an actual DCECT, a series of field experiments is carried out in a convertor station in China Southern Power Grid. Both the input signal and output signal are recorded for modelling. Furthermore, all the constant harmonic experiments are applied to model DCECT, which concludes a transient model including shunt impedance, low-pass filter and constant time delay by digital circuits. At last, the proposed model is verified by the step responses measured in field experiment, which have a quite similar output as the actual DCECT.