A capacitive sensor for assessing early degradation of transformer insulation by detecting 2-furfuraldehyde (2-FAL) at the sub-ppm level in transformer oil is presented in this paper. The sensor uses a molecularly imprinted polymer (MIP) in which 2-FAL sensitive receptors are created. The 2-FAL molecules in the oil are adsorbed on the receptor cavity of the MIP which results in a change in the sensor capacitance. The sensing film is prepared by the sol-gel technique using methacrylic acid, divinyl benzene, and azobis. The sensor is successfully tested from sub-ppm to ppm of 2-FAL concentration. The average sensitivity of the sensor is 0.379 pF/ppm, and the average standard deviation is 0.035 pF at 1 kHz in the range of 0–10 ppm. The sensor shows piecewise linear characteristics for sub-ppm and higher ppm ranges. The resolution of the sensor is 0.1 ppm in the sub-ppm range, and hence, it can be used for anticipating early failure as well as provide warning during an advanced stage of deterioration. The average repeatability index of the sensor is ±0.033%, which indicates negligible drift and stability of sensing film.

中文翻译：

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通过感测变压器油中的 2-FAL 来检测绝缘退化的电容式传感器

本文介绍了一种电容式传感器，用于通过检测变压器油中亚 ppm 级的 2-糠醛 (2-FAL) 来评估变压器绝缘的早期退化。该传感器使用分子印迹聚合物 (MIP)，其中产生了 2-FAL 敏感受体。油中的 2-FAL 分子吸附在 MIP 的接收腔上，导致传感器电容发生变化。传感膜是通过溶胶-凝胶技术使用甲基丙烯酸、二乙烯基苯和偶氮双制备的。该传感器已成功测试从亚 ppm 到 ppm 的 2-FAL 浓度。传感器的平均灵敏度为 0.379 pF/ppm，平均标准偏差为 0.035 pF，频率为 1 kHz，范围为 0–10 ppm。该传感器显示了亚 ppm 和更高 ppm 范围的分段线性特性。传感器分辨率为0。1 ppm 在亚 ppm 范围内，因此，它可用于预测早期故障以及在恶化的晚期阶段提供警告。传感器的平均重复性指数为±0.033%，表明传感膜的漂移和稳定性可以忽略不计。