Factors Affecting the Flow Electrification of the Liquid Nitrogen in HTS Transformers and Its Suppression Methods

Polyimide (PI) film is extensively utilized in high-temperature superconducting (HTS) transformers due to their excellent electrical properties, but their friction with liquid nitrogen (LN) generates static charges. The buildup of a substantial quantity of electric charge causes it to discharge on the surface of the PI film, resulting in harm to the transformers’ insulation. So, it is very necessary to carry out prophylactic tests for the electrostatic charging tendency of the LN. In this article, the streaming electrification of the LN can be generated and measured via the spinning disk system. The characteristics of LN flow electrification are explored, then, the PI films modified by nano-Al2O3 are prepared with different mass fractions, and the influencing factors on the electrification are discussed. A transformer LN flow channel model was established, and finite element analysis was used to analyze the electric field distribution inside the LN pipeline made of PI films. Studies indicate that the diameter and rotational velocity of the disk and the content of nanoparticles are the primary elements that influence the electrification current, and owing to the constant accumulation of the charges, serious electric field distortion can occur inside the pipeline. The study findings can offer a novel idea for predicting the electrostatic charging trend of LN.