Influence of impregnating liquids on dielectric response of impregnated cellulose insulation

The dielectric response of cellulose in the form of paper and pressboard was investigated. Samples of pressboard were impregnated with different insulating liquids: new and aged transformer oil and synthetic ester. Samples of non-impregnated paper were investigated during drying process. The research was done for two groups of pressboard with about 5 % and 0.5 % moisture content. The moisture level was determined using Karl Fischer titration. Obtained data were analyzed using Havriliak-Negami relaxation function. The results can be useful for moisture evaluation in various impregnated cellulose insulations e.g. transformers, bushings, capacitors.