Interaction Between Electric Field Profile and Partial Discharges Simultaneously Detected in a Loaded HVDC Cable: Space Charge Analysis

The aim of this work is to evaluate the correlation between electric field distribution and the onset of partial discharge. The specimen under test is a DC model cable containing an air void defect and subjected to both electrical stress and thermal gradient. The electric field distributions have been calculated starting from the space charge detected by means of a novel PEA cell. While, the partial discharge activity has been monitored by means of the PryCam sensor. The space charge and partial discharge phenomena have been simultaneously acquired in order to make clearer the interaction between both phenomena. Measurement results show that the electric field distribution along the radial direction of the cable is variable over time. The initial Laplacian distribution of the field results inverted after 20 minutes of voltage application. After this time interval, the electric field in the external cable radius, where the air void defect is located, is increased. Therefore, the partial discharge inception electric field within the defect results reached and equal to 17.8 kV/mm in the healthy cable section. This paper represents the first part of this investigation and it is focused on the description of the novel PEA cell, on the explanation of the measurement setup and on the evaluation of the obtained charges and electric field distributions. The second part of this study, instead, is focused on the analysis and description of the observed partial discharge activity.