Preliminary Space Charge Characterization of Polypropylene-based Compounds for HVDC Cable Insulation

In recent decades, with the growing importance of clean and renewable energy, High Voltage Direct Current (HVDC) technology has made significant progress. Among the parameters related to the cables, the build-up of space charge leads to a concentrated rise in the electric field strength, which speeds up the aging of the insulating materials used in cables. Moreover, HVDC cable life and reliability models should encompass all service stresses, including the effects of localized space charge distributions which is a key factor to evaluate the health of cable insulation. Therefore, it is important to create new insulation materials for next generation HVDC cables that have less accumulation of space charge. In 2022, the development of cable manufacturing with thermoplastic insulations made from a newly-developed Polypropylene (PP)-based compound has been encouraged by the European Union's Horizon 2020 research and innovation program. This is because PP-insulation compounds are very stable at high temperatures, lower price, lower weight, simpler manufacturing, and can be easily recycled. The main focus of this thesis is to determine the distribution of space charge density, polarization and depolarization periods, field enhancement factor (FEF), and trap distribution using data from space charge measurements. The PEA method was chosen because it is suitable for a wide range of sample geometry (thin and thick samples) to generate simulated raw PEA output data, with a particular emphasis on thermoplastic polypropylene (PP)-based insulation for flat specimens. The findings show how space charge accumulates in the flat specimens and undergoes significant changes as the material ages. Through a simple experimental method, this approach allows us to comprehend how charges become trapped and released in polymer materials. Additionally, it helps to identify significant indicators of store space charge and maximum electric field in these materials.