基于光纤S锥的电力变压器油中微水传感研究

Research on Moisture Sensing in Power Transformer Oil Based on S-shape Optical Fiber

微水含量是衡量油浸式变压器绝缘性能的一个重要技术参数,实时跟踪变压器油中微水含量对保障油浸式变压器乃至整个电力系统稳定运行具有重要意义。为此,该文提出一种基于光纤S锥的微水传感技术。通过分析S锥形光纤的物理模型,构建S锥引起光强衰减与微水含量的量化关系,并利用光束传输法分析光纤S锥光束传播过程,评估锥腰直径、轴向偏移量等参数对S锥中基模、高阶模之间耦合程度以及高阶模的占比程度和持续长度的影响。制备不同结构参数的S锥光纤传感器,并开展不同微水含量的变压器油样中实测。结果表明,S锥光功率衰减幅值随油中微水含量增加而增加,S锥锥腰直径越细、轴向偏移量越大,对应S锥的检测灵敏度越高。对于锥腰直径为30μm、轴向偏移量为60μm的S锥光纤探头,检测下限达到4.67mg/L。可知,S锥传感器可有效实时跟踪变压器油中的微水含量,有助于及时发现变压器早期存在的绝缘受潮问题,保障其长期安全运行。

Moisture content is an important technical parameter to measure the insulation performance of oil-immersed transformers.Real-time tracking of the moisture content in transformer oil is of great significance to ensure the stable operation of oil-immersed transformers and even the entire power system.For this reason,this paper proposed a moisture sensing technique based on S-shape optical fiber.By analyzing the physical model of the S-shape fiber,the quantitative relationship between the light intensity attenuation caused by the S-shape fiber and the moisture content was established.And the beam propagation process of the fiber S-taper was analyzed by the beam propagation method(BPM),and the cone waist diameter,axial offset,etc.The influences on the coupling degree between the fundamental mode and higher-order modes in the S-shape cone and the proportion and duration of higher-order modes were evaluated.Then S-shape optical fiber sensors with different structural parameters were prepared in the lab,and actual measurements in transformer oil samples with different moisture content have carried out.The results show that the optical power attenuation amplitude of the S-shape cone increases with the increase of moisture content in the oil.The smaller the diameter of the S cone waist diameter and the larger the axial offset,the higher of detection sensitivity of the S-shape fiber sensor.For the S-shape fiber probe with a waist diameter of 30μm and an axial offset of 60μm,the lower detection limit reaches 4.67 mg/L.Therefore,the S-shape fiber sensor can effectively track the moisture content in the transformer oil in real-time,which helps to detect the insulation damp problem in the early stage of the transformer in time and ensure its long-term safe operation.