Model Study of VDC ELlectric Field Effect

Energized scale models of HVDC transmission lines and converter stations can be used as design tools to determine the electric field distribution in their vicinity. To prove the method, energized scale models of a ±400-kV HVDC test line and of the Arrowhead ±250-kV converter station have been designed and built in order to compare the electric field distribution of the full-scale facilities with that of the models. Linear scale factors were 1/50 for the line and 1/33.33 for the station. The paper reviews instrumentation, modeling and scaling problems and their solutions: calibration and verification test; and discusses the accuracy of the model measurements. Comparison of corresponding ground level electric field strength test ranges shows that the agreement between full-scale and model measurements is good. Techniques were developed for full- scale and model conductor tests in laboratories, and for field and model experiments. An experimental method (the method of images) of determining the corona onset voltage of actual bipolar HVDC transmission lines with single conductors was developed. Additional experiments were conducted in various areas of the model converter station. Features studied were: electric field and ion current profiles under energized and partially deenergized conditions, effects of ground wires, and effects of shielding. The feasibility of worst case open-circuit voltage and short-circuit current measurements on model objects and vehicles was demonstrated.