Abstract

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*(ω) 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*(ω) 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*(ω) 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*(ω), 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 (τ_M) and integral value (IV) of the real part of M*(ω) are less than 8%. In that respect, the novelty of this work is that the τ_M and IV might be used as a potential tool for quantitative evaluation of mc% of cellulose insulation in paper/oil systems.

Graphic abstract

抽象的

基于频率介电谱（FDS）技术的纸/油系统中的纤维素绝缘材料的水分评估已引起研究人员的极大兴趣。但是，电极极化效应和电导效应会在传统FDS测试过程中“模糊”松弛信息，这通常会导致结果不可靠。现有研究表明，频率介电模量M *（ω）可以有效地研究松弛行为，可用于实现纸/油体系中纤维素绝缘材料的状态评估。不幸的是，很少使用M *（ω）来评估水分含量（mc纤维素绝缘材料的百分比），基于M *（ω）提取特征参数的方法的研究也很少。鉴于此问题，本贡献试图报告一种可用的基于M *（ω）提取特征参数的方法，并进一步研究mc％与上述参数的变化规律。这些发现揭示了mc之间的定量关系。％和上述参数可以通过拟合分析来建立。新制备的纤维素绝缘样品证明了所提出的参数用于评估纤维素绝缘材料的水分的可行性。有趣的是，注意，对应于弛豫时间常数（评估结果的平均百分比误差τ_中号）和积分值（IV的实部）中号*（ω）小于8％。在这方面，这项工作的新颖性在于，在τ_中号和IV可以被用作用于定量评价的潜在工具的MC在纸/油系统纤维素绝缘的％。

图形摘要