PETROLEUM PROCESSING AND PETROCHEMICALS ›› 2025, Vol. 56 ›› Issue (2): 116-122.

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CHANGE OF COMPOSITION OF TRANSFORMER OIL UNDER HIGH VOLTAGE ELECTRIC FIELD

  


  • Received:2024-08-07 Revised:2024-10-16 Online:2025-02-12 Published:2025-01-16

Abstract: In order to investigate the change of transformer oil composition and its insulation performance under partial discharge, the transformer oil after nitrogen or hydrogen purging (replacing dissolved gas in oil) was carried out discharge test under the high voltage electric field, and the change of density, viscosity, carbon type composition and hydrocarbon group composition of transformer oil after different ionization time was observed. The results show that the density and viscosity of transformer oil increase gradually with the increase of ionization time, which indicates that macromolecular substances with higher molecular weight are formed in transformer oil under the electric field. With the increase of ionization time, the aromatics content of transformer oil gradually decreases and the naphthene content gradually increases, which indicates that under the high voltage electric field, the aromatics in transformer oil will transform into naphthene. With the increase of ionization time, the content of alkanes in the saturated hydrocarbon of transformer oil decreases slightly, and the content of cycloalkanes increases slightly. In naphthenic hydrocarbons, the content of monocyclic to tricyclic cycloalkanes decreased slightly, while the content of tetracyclic and pentacyclic cycloalkanes increased slightly. In aromatic hydrocarbons, the content of bicyclic aromatic hydrocarbons decreased significantly, while the content of monocyclic aromatic hydrocarbons increased significantly. The dielectric loss factor of transformer oil increases and the anti-gassing property decreases, indicating that the insulation property of transformer oil decreases with the increase of ionization time.

Key words: transformer oil, high voltage electric field, ionization, hydrocarbon composition