Effect of Space charge accumulation inside the thermoplastic insulation of a loaded HVDC model cable

The space charge accumulation phenomenon represents one of the main degradation factors for the dielectrics employed in the field of the HVDC transmission. For this reason, the recommendation IEEE Std 1732-2017 has been proposed. In that standard, due to the importance attributed at the space charge phenomenon, the experts suggest the introduction of the space charge measurement in HVDC cables during the prequalification or type tests, by means of the PEA method. However, despite for tests in flat specimens the PEA technique is well consolidated, for cable specimens difficulties are still present. In particular, the PEA cell output signal is strongly conditioned by the arranged measurement setup, such as the connection between the components and ground, the length of the cable specimens under test, the position and the width of the pulse voltage electrodes. Based on the above, the aim of the present work was to arranged a PEA measurement setup in order to obtain a clear charge profile. In addition, considering that the above mentioned standard requires the space charge measurement also under temperature gradient, in our work this has also been made.