The Dielectric Voltage Response Characteristics of Transformer Oil–Paper Insulation and Its Aging State Assessment

The dielectric voltage response characteristics of transformer oil–paper insulation are closely related to aging and moisture. Polarization voltage rate and degradation voltage rate can be used to evaluate insulation aging and moisture, respectively, but it takes a long time to acquire the above two characteristics. In this paper, the dielectric voltage response characteristic of transformer oil–paper insulation was measured by a single charge and multiple discharge method. The change rule of its initial slope characteristic was analyzed based on the relationship between the attenuation amplitude of dielectric polarization intensity reflected by the equivalent circuit and the initial slope of dielectric voltage response. The cumulative sum of initial slopes of dielectric voltage response (S) is proposed to evaluate the aging state of transformer oil–paper insulation. At the same time, the corresponding relationship between the characteristic quantity S and the content of furfural (Ck) in oil is studied experimentally. The results show that with the increase of insulation aging degree, both Ck and S increase. The fitting results show that the proposed characteristic quantity S and Ck have a linear relationship suitable for quantitative analysis of the insulation aging state.