Extracting Frequency Spectroscopy of Oil-Immersed Paper Based on Havriliak–Negami Model Without Known Insulation Structure of Transformer
Qingchuan Xu, Shengkang Wang, Fuchang Lin, Hua Li
Abstract
When using the Frequency Dielectric Spectroscopy (FDS) method to evaluate the insulation condition of a transformer, it is essential to calculate the frequency spectroscopy of the oil-immersed paper from the major insulation of transformer with the structural parameters. However, in on-site measurement, the structure of the transformer is often unknown, which greatly limits the application of the FDS method. This paper proposed a method for extracting the frequency spectroscopy of oil-immersed paper from the oil-paper insulation without the known insulation structure. Firstly, the frequency spectroscopy of the oil-immersed paper with different moisture content, aging states, and temperatures was measured and analyzed. The results showed that the Havriliak-Negami (H-N) model with hopping conductivity is the most suitable frequency spectroscopy model for the oil-immersed paper in different conditions. Secondly, the transformer insulation model was constructed, and the frequency spectroscopy of the corresponding oil-immersed paper was calculated. The calculation showed that the error of the structural parameters influences the calculated frequency spectroscopy of oil-immersed paper, especially in the low moisture condition, which leads to the increase of the fitting residual of the H-N model. According to the smallest fitting residual, the structural parameters can be analyzed, and the frequency spectroscopy of oil-immersed paper can be extracted accurately from the oil-paper insulation without the known insulation structure.