Aging characteristic parameter extraction of oil-paper insulation based on frequency domain spectroscopy

Oil-paper insulation is widely used in power transformers. Thus, its insulation quality, aging included, has a strong impact on the operation of power transformer. The purpose of this paper is to evaluate oil-paper insulation's aging condition more reliably. The frequency domain spectroscopy of several oil-immersed paper samples with different aging conditions were measured at 25°, 60°, 90° and 120°. Some characteristic parameters were extracted based on a proposed dielectric response function model. Results show that reconstructed curves got from the proposed model were in good agreement with measured curves. Aging and temperature can not only make a difference on the polarization process in high frequency domain, but also can influence the conductance process in the low frequency domain. It's concluded that relaxation time t and shape parameters β and γ can be selected to analyze the aging degree of oil-immersed paper, while DC conductivity σ
₀
and relaxation time t can be modified to eliminate the influence of temperature.