Experimental Analysis of Thermal Methods on the Distribution of Space Charges in Medium Voltage Cables

Measuring space charge is an important aspect of understanding the behaviour of electrical insulation systems, particularly in high-voltage applications. This experimental work focuses on the study of medium-voltage cable sections for which a specific tray, designed for their cylindrical shape, has been developed. In addition, the processing of experimental data to determine the distribution of space charges was the subject of specific mathematical development. This approach was applied to the analysis of a batch of medium-voltage cable samples that had previously been aged for 1,300 hours at 70 kV DC. Thermal waves are generated by the Joule effect in the cable screen. It moves from the shield to the cable core. This approach has enabled us to deepen our understanding of the mechanisms involved and to gain a better grasp of the evolution of space charges under these specific operating conditions, revealing the presence of space charges near the cable core. In our study, we used two different methods to heat the cable under test. The initial strategy involved the application of incessant heat for a duration of 30 seconds, while the subsequent technique adopted a pulsed heat mode, fluctuating at intervals of 1 second, 2 seconds and 3 seconds respectively. Thus, this study aims to explore and highlight crucial aspects of space charges in insulators under high stress, highlighting their implications for the performance and durability of materials used in advanced electrotechnical and electronic applications.