Measurements of leakage current and field enhancement in extruded model cables at HVDC

In the characterization of insulation materials for extruded HVDC cables, measurements of leakage current and space charge distribution are often used. The apparent conductivity that can be obtained from leakage current should be in agreement with the conductivities that can be evaluated from the time evolution of space charge from voltage application until steady-state. In this paper, examples of leakage current data and space charge data for two cables having different levels of conductivity are presented. The similarities in the results are shown, and differences as well as future challenges are discussed.