Review of space charge measurements in high voltage DC extruded cables by the thermal step method

More than ever, controlling the amount of space charge that accumulates in high voltage DC (HVDC) extruded cables under electrical stress and a thermal gradient is a major challenge to ensure a good level of reliability of the cable and therefore a good availability of energy [1]. It is now clear that, although studies on space charge are absolutely necessary to understand the charge accumulation and relaxation phenomena, direct measurements on power cables are required to analyze and anticipate the local electric field. Thus, measurement of the electric field due to the presence of space charge within the insulation is essential for an optimal design of power cables [2]. In this article, after detailing the principle of the TSM applied to a power cable, some examples of research performed on power cable specimens in an academic research laboratory are given. In addition, technology transfer to industry, and recent measurements of space charge and electric field distribution in a HVDC extruded cable insulation, in an industry laboratory, are presented.