A mechanical characterization and chemical compatibility assessment of semiconducting tapes for power transformer applications

This research project aims to evaluate the suitability of the Poseco composite tape as a replacement for the semiconductive tape Asecond 1.0 used in power transformer core banding. The assessment includes chemical compatibility testing between selected tape ma terials and typical transformer cooling, including mineral oils, and ester-based oils; mechanical characterization through tensile and shear tests at 20 °C and 105 °C; thermo-mechanical analysis via DMA; numerical modeling through FEM simula tions; and electrical measurements. Both materials comply with chemical compatibility requirements, showing no oil degradation in FTIR spectra. Poseco induces a limited reduction in the interfacial tension of mineral oil, 46 to 39 mN/m, still above the 30 mN/m threshold. Mechanically, Poseco exhibits higher longitudinal stiffness, with Young’s modulus of 19.3 GPa at 20 °C, compared with 14.3 GPa for Asecond 1.0. However, Poseco displays significant post curing brittleness and fiber separation. The main limitation is the electrical behavior: Asecond 1.0 shows resistance val ues consistent with semiconductive behavior: 1.6–15.2 kΩ. Poseco, instead, exhibits much higher values: from 950 kΩ up to 2.3 MΩ. So further tests are required to clarify this critical aspect.