Fundamental studies of the influence of the morphology of cross-linked polyethylenes on the accumulation and mobility of space charges

• Applicants: Professor Dr.-Ing. Frank Jenau; Privatdozent Dr. Frank Katzenberg
• Subject Area: Electrical Energy Systems, Power Management, Power Electronics, Electrical Machines and Drives ; Synthesis and Properties of Functional Materials
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 540115060

Cross-linked low-density polyethylene (xLDPE) has established itself as an organic insulating material for the insulation of AC components in the field of high-voltage technology due to its largely non-polar character, high volume resistance and low loss factor. Due to the change of power flow caused by the energy transition, high-voltage direct current transmission is used as a solution for long distance power transmission in German grid development planning. This changes the electric field stress in used dielectrics. It is known that polymer insulating materials tend to accumulate space charges under high DC field stress. From the point of view of component design, this must be avoided, since the dielectric is subjected to additional field loading, which in turn leads to increased aging of the polymer and thus to a reduction in the lifetime of the component. Preliminary work shows, that the accumulation of space charges in xLDPE can be influenced by its structure and morphology. The goal of this project is to fundamentally investigate the interactions between the structure and morphology of xLDPE and the formation, accumulation and mobility of space charges under high DC stress. Since, especially in the case of cross-linked polyethylenes, not only the structure (degree of branching, degree of cross-linking) but also their morphology (type, arrangement and orientation of crystals, crystallinity, orientation, etc.) and, consequently, their thermal properties (relaxation temperatures, melting temperature) can be influenced within wide limits, xLDPE test specimens with a defined structure and morphology will be produced, analyzed with the pulsed electro-acoustic method (PEA) regarding the space charge accumulation, and structure-property relationships will be derived. Cooperative collaboration of polymer science and high voltage engineering is required for realizing this project.

• DFG Programme: Research Grants