Insulation condition diagnosis of transformer with multi-peak polarization spectrum

Return voltage measurement is an effective dielectric response test method and has been used to evaluate aging condition of solid insulation. The dominant time constant is one of the most common characteristic quantities for assessing the moisture of the transformer. However, the return voltage curve maybe appear multiple peaks due to many factors in the process of field test, which affects the accurate judgment of the dominant time constant, therefore, it is difficult to evaluate transformer solid insulation condition by polarization spectrum and the dominant time constant. This paper analyzes the relationship between the return voltage characteristics and parameters of the equivalent circuit based on extended Debye model to better understand the variation rule of the polarization spectrum. According to the simulation results, some new ideas of diagnosing solid insulation condition are proposed. The results show that the method proposed in this paper is reasonable and effective.