Abstract

Oil-immersed cellulose insulation is the heart of the power transformer, which will will gradually deteriorate in the operation process of transformer. Therefore, accurately evaluating the aging condition of the oil-immersed cellulose insulation is important for maintaining safe and stable operation of transformer. In this paper, the synergistic effect of moisture and aging on frequency dielectric spectroscopy (FDS) of oil-immersed cellulose insulation was analyzed in depth using the modified cole–cole model. A novel degree of polymerization (DP) evaluation method for oil-immersed cellulose insulation based on the dielectric modulus analysis and its curve translation method was proposed. Results show that the higher the moisture content and the lower the DP, the greater the frequency dielectric parameters, the smaller the α relaxation time, the greater the DC conductivity and hopping conductivity of the oil-immersed cellulose insulation. The novel DP evaluation method for oil-immersed cellulose insulation based on calculating the integral area of the imaginary part of dielectric modulus A_(DP–mc%) and translating the A_(DP–mc%) curve was proposed, which could simultaneously consider the synergistic effect of moisture and aging on FDS. The novel DP evaluation method for the oil-immersed cellulose insulation is suitable for moisture range is 0.5–5%, and the DP range is 250–1300. The verified effectiveness of the novel DP evaluation method presents that it is ideal for transformer aging condition assessment, which is superior to the existing evaluation methods.

Graphic abstract

中文翻译：

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水分和老化对油浸纤维素绝缘材料的频率介电响应的协同增强作用及其使用介电模量的聚合度评估

摘要

油浸纤维素绝缘是电力变压器的心脏，它将在变压器的运行过程中逐渐恶化。因此，准确评估油浸式纤维素绝缘的老化条件对于维持变压器的安全稳定运行非常重要。在本文中，使用改进的cole-cole模型深入分析了水分和老化对油浸纤维素绝缘材料的频率介电谱（FDS）的协同效应。提出了一种基于介电模量分析的油浸纤维素绝缘聚合度评价方法及其曲线平移方法。结果表明，水分含量越高，DP越低，频率介电参数越大，α弛豫时间，油浸纤维素绝缘体的直流电导率和跳跃电导率越大。提出了一种新的油浸纤维素绝缘DP评估方法，该方法基于计算介电模量A _{（DP–mc％）}虚部的积分面积并转化A _{（DP–mc％）}曲线，该方法可以同时考虑水分和老化对FDS的协同作用。用于油浸纤维素绝缘的新型DP评估方法适用于水分范围为0.5–5％，DP范围为250–1300的情况。经验证的新型DP评估方法的有效性表明，它是变压器老化条件评估的理想选择，优于现有评估方法。

图形摘要