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荧光光纤温度传感器长期浸没在变压器油中,随着使用时间的增加,其护套材料不可避免地会经历老化过程。通过有限元仿真发现荧光光纤温度传感器及其护套在工作时所处的电场很小,热老化是护套材料老化的主要形式。为此,针对荧光光纤温度传感器的3种不同护套材料即交联聚烯烃、聚氨酯和聚氯乙烯,在不同温度的变压器油中进行了热老化;然后使用Fourier变换红外光谱(Fourier transform infrared spectroscopy,FTIR)对试样的化学结构进行了辅助分析,并且基于机械拉伸实验和使用沿面电极布置形式的等温松弛电流方法,对不同护套材料的老化状态进行了分析评估。红外光谱实验结果表明:交联聚烯烃和聚氨酯护套在变压器油中热老化后均发生一定程度的分解,聚氯乙烯护套的红外光谱在老化前后没有大的变化。机械拉伸实验结果表明:交联聚烯烃护套的断裂伸长率和拉伸强度都大幅下降,聚氨酯护套的断裂伸长率下降但是拉伸强度却增加,而聚氯乙烯护套的断裂伸长率和拉伸强度均没有太大变化。等温松弛电流方法计算结果表明:老化后各种护套的老化因子值均大于未老化护套的值。综合评估可得:交联聚烯烃护套在油中热老化性能最差,聚氨酯护套次之,聚氯乙烯护套性能最好。
Fluorescent optical fiber temperature sensor immersed in transformer oil for a long time, with the use of time increases, the sheath material will inevitably undergo the aging process. Finite element simulation found that the optical fiber temperature sensor and its sheath in the working place where the electric field is very small, thermal aging is the main form of sheath material aging. For this reason, three kinds of sheathing materials, ie, cross-linked polyolefins, polyurethanes and polyvinyl chloride (PVC) for fluorescent fiber temperature sensors were thermally aged in transformer oil at different temperatures. Fourier transform infrared spectroscopy , FTIR) were used to analyze the chemical structure of the samples. The aging behavior of different jacketing materials was evaluated based on the mechanical tensile test and the isothermal relaxation current method using the surface electrode arrangement. Infrared spectrum experimental results show that: crosslinked polyolefin and polyurethane jacket in the transformer oil heat aging after a certain degree of decomposition, the infra-red spectrum of PVC jacket before and after aging did not change significantly. Mechanical tensile test results show that: the elongation at break of the crosslinked polyolefin sheath and tensile strength are significantly reduced, the elongation at break of the polyurethane sheath decreases but the tensile strength increases, and the fracture of the PVC sheath Elongation and tensile strength are not much changed. Isothermal relaxation current method results show that: after aging all kinds of sheath aging factor values are greater than the value of unaged sheath. Comprehensive assessment available: cross-linked polyolefin jacket in the worst thermal aging properties, followed by polyurethane jacket, PVC jacket best performance.