Quantitative evaluation for moisture content of cellulose insulation material in paper/oil system based on frequency dielectric modulus technique

The moisture evaluation of cellulose insulation material in paper/oil system based on the frequency dielectric spectroscopy (FDS) technique has been of great interest to researchers. However, the electrode polarization effect and conductance effect can "obscure" the relaxation information in the course of the traditional FDS test, which often leads to an unreliable result. The existing researches indicated that the frequency dielectric modulus-M*(omega) could effectively enable the investigation of the relaxation behavior, which might be used to realize the condition evaluation of cellulose insulation materials in paper/oil system. Unfortunately, the M*(omega) has been rarely exploited to evaluate the moisture content (mc%) of cellulose insulation material, and the study on approach for extracting characteristic parameters based on the M*(omega) is also rare. In view of this issue, the present contribution attempt to report an available approach for extracting the characteristic parameters based on the M*(omega), and further investigate the variation laws of mc% versus the above parameters. The findings reveal that the quantitative relationship between mc% and the above parameters can be established by fitting analysis. The feasibility of the proposed parameters for moisture evaluation of cellulose insulation material is demonstrated by the newly prepared cellulose insulation samples. It is interesting to note that the average percentage errors of evaluation results corresponding to the relaxation time constant (tau(M)) and integral value (IV) of the real part of M*(omega) are less than 8%. In that respect, the novelty of this work is that the tau(M) and IV might be used as a potential tool for quantitative evaluation of mc% of cellulose insulation in paper/oil systems. Graphic abstract