Predictability of PD inception in defects included in HVDC cables by conductivity models calibrated through experiments

To date, there are several methods for calculating the electric field distribution within a dielectric layer subjected to HVDC voltage. However, experimental techniques for evaluating the accuracy of models for calculating the electric field, such as space charge measurement, are often not precise enough to be used for this purpose. At the same time, the knowledge of Partial Discharge (PD) phenomenon occurring under HVDC stress is also not as developed as that of PD under HVAC voltage. The main goal of this research is to study the effectiveness of dielectric conductivity models to forecast the inception condition for PD under load and HVDC voltage stress. This study has been carried out by means of comparison between computer simulation and experimental results. The simulations have been carried out by means of a dielectric conductivity model implemented in the FEM software Comsol Multiphysics. The experimental setup consist of a model cable insulated with XLPE with an artificial defect created at the outer surface of the dielectric layer. Although the definition of the electric field inside a cavity is affected by several parameters which are also mutually dependent, the analysis performed demonstrates the predictability of the PD activity within certain voltage and temperature ranges.