Long-Term Behavior of Electrical Properties under Combined Thermal, Water and Electrical Stress of Low Voltage PVC Cable Insulations for DC applications

• Applicants: Professor Dr. Frank Berger; Professor Dr. Stefan Kornhuber; Professor Dr.-Ing. Florian Puch
• Subject Area: Electrical Energy Systems, Power Management, Power Electronics, Electrical Machines and Drives
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 559008720

The usage of DC is not limited to high voltage energy transport over long distances like the HVDC links in seas or from the coast to the southern part of Germany. The LVDC and MVDC applications will cover a broad variation of different areas from industry, mobility to household. Plasticized PVC of various mixtures is dominantly used for cable insulation in low voltage applications because it is cheap and its mechanical, electrical and chemical properties are sufficient, when the mixture is suitable for the intended use. Results of the research project DC-Industrie 2 show different behavior of different PVC-based cable insulations. It can be hypothesized that additives and fillers present in the PVC compounds play a significant role for the long-term behavior of the insulation.Especially the interaction with the electric field leads to a different behavior at AC and DC stress. However, during the operational stress the constant and unidirectional electrical field is leading to different effects and therefore different stresses compared to AC applications: Electrophoresis becomes an effect that has to be considered for DC applications. Also, electro-chemical processes may force corrosion on conductors, especially in the presence of waterIdentifying and quantifying the main factors for degradation and therefore contribution to long-term behavior of PVC-based insulation materials for low voltage cables under combined electrical, thermal and water stress has been identified as a significant research gap.Based on the preliminary work, material components (plasticizer, filler, stabilizer, …) and the environmental conditions were identified to play a significant role. It is intended to control the compound matrix and environmental conditions in order to separate the influence of the factors in terms of long-term electrical behavior. For the proposed project, the polymer matrix is reduced to the dominant components relevant for cable insulations: PVC, plasticizer and CaCO3 Closing this research gap is of great importance for dealing with the opportunities of increasing possibilities of low voltage DC application and networks and a possible transfer of existing networks from AC to DC. The investigations contribute to the general understanding of materials and endurance. In addition, the electrical behavior can be described mathematically by means of network models. For defined conditions, the use of a PVC compound is reduced to limited, specific additives: CaCO3 and plasticizer.

• DFG Programme: Research Grants