Quantitative aging assessment method for cellulose pressboard based on the interpretation of the dielectric response mechanism

Abstract

Cellulose pressboard is used as a key element in various power equipment insulation structures and determines the operational safety of electric equipment and power systems. This paper aims to increase the application of a pressboard aging assessment method based on frequency domain spectroscopy, a promising nondestructive method for power equipment diagnosis, through in-depth theoretical analysis and accurate data fitting. To achieve this purpose, first, based on classic theoretical models in the field of dielectric physics, a mathematical deduction is proposed to separate each dielectric process in the overlapping frequency band. Second, a novel analysis approach that considers both the pressboard dielectric response and the thermally stimulated current is proposed and demonstrated to be effective in determining the physical meaning of pressboard microscopic dielectric processes. Third, a function model based on a specific microscopic mechanism is established to fit the frequency domain spectra of pressboard samples with different aging degrees. Based on this approach, the variations in charge carrier motion characteristics in the frequency domain with increasing pressboard aging degree are clarified. Moreover, the function model provides characteristic parameters that are clearly related to the degree of polymerization of the material, which represents a quantitative method for evaluating the aging degree of cellulose pressboard by indirectly obtaining its frequency response curve.