Investigation on the Electrical Properties of Branched Lipophilicity Palmitic Acid‐Modified Polyimide Oil Paper Structures

ABSTRACT Oil‐paper insulation, as the main dielectric medium in transformers, directly affects the operational safety and stability. To enhance the lipophilicity properties of cellulose‐based insulating paper, a palmitic acid side‐chain grafted polyimide resin (TPI‐PA) was designed and synthesized in this study, and the TPI‐PA insulating paper was fabricated via electrospinning. Through Fourier transform infrared spectroscopy (FT‐IR) and nuclear magnetic resonance (NMR) characterization and analysis, it was confirmed that the lipophilic palmitic acid long‐chain structure had been successfully grafted to the polyimide main chain. The performance test results show that when the palmitic acid content is 15 wt%, the AC breakdown field strength reaches 68.65 kV mm −1 , which is about 70.87% higher than that of the traditional lignocellulosic paper. By virtue of molecular energy band structure calculations, high‐temperature DC conductivity measurements, and surface potential decay characterizations, the TPI‐PA insulating paper/transformer oil composite system is demonstrated to suppress carrier migration dynamics and mitigate internal space charge accumulation, thereby achieving a pronounced enhancement in the electrical performance of the composite insulation assembly. Furthermore, the polyimide‐based insulating paper reinforces the wettability at the oil‐paper interface, which not only curtails the propensity for partial discharge but also endows the insulating paper with remarkably improved lipophilicity. Collectively, this work furnishes novel insights into the material optimization strategy for oil‐paper composite insulation systems in transformers, which is of considerable significance for the advancement of high‐performance insulating materials in power equipment.