Two Models for Predicting Frequency-Domain Spectroscopy of Nonuniformly Damped OIP Bushings Based on FEM and Dielectric Theory

Frequency-domain spectroscopy (FDS) is a nondestructive technique for moisture status evaluation of oil-impregnated paper (OIP) bushings; however, due to the lack of effective models to predict the FDS curve of OIP bushings under nonuniform moisture, it is difficult to establish a large database for FDS characteristics analysis and heterogeneous moisture status assessment. To address this issue, this article established a bushing finite element method (FEM) model and an improved X model based on the FEM and dielectric theory, respectively, for FDS prediction of nonuniformly damped OIP bushings. Comparing the FDS curves predicted by the bushing FEM model and the improved X model, it was found that the average relative errors are less than 1.25%. Finally, FDS measurements were conducted on the nonuniformly damped bushings in the laboratory to verify the accuracy of the proposed models. The experimental results indicated that the average relative errors of the bushing FEM model and improved X model in FDS prediction are less than 9.29% and 10.21%, respectively. This proves that the proposed models are highly accurate. The innovation of this article lies in establishing a bushing FEM model and an improved X model to predict the FDS curve of OIP bushings under nonuniform moisture.