An improved second-order kinetic model for degradation analysis of transformer paper insulation under non-uniform thermal field

Abstract

The ageing kinetic model is regarded as an effective tool to describe the degradation of transformer paper insulation. However, the temperature of the transformer winding is unevenly distributed, and the existing ageing kinetic models only depend on experimental data of accelerated thermal ageing at a constant temperature. Given this issue, this work proposes an improved second-order kinetic model accounting for the non-uniform thermal field. First, oil-paper insulation samples with different ageing stages are prepared under the non-uniform thermal field. Then, the sample's experimental data of moisture dispersion and distribution of degree of polymerisation are collected. On this basis, the improved second-order kinetic model is derived to simulate insulating paper's ageing process subjected to an axial temperature gradient. Further, the relationship of the parameters in the improved second-order kinetic model with the temperature and moisture content at different winding heights is obtained. Finally, the proposed model is validated, and the results show that the proposed model is more scientific than the traditional models to describe the degradation of paper insulation. In that respect, this work illustrates an improved second-order kinetic model to provide a reference for the ageing assessment/life prediction of transformer paper insulation under the non-uniform thermal field.