基于核磁共振弛豫谱的变压器油老化检测研究

针对目前常规的变压器油绝缘热老化检测中过程繁杂等问题, 提出一种基于低场核磁共振弛豫时间谱的检测方法。根据油品中烃类化合物在高压放电环境中出现裂解、结构发生改变的原理, 设计变压器油热老化核磁共振横向弛豫谱检测系统。采用自旋回波序列采集油样时域信号回波峰值点, 描述弛豫时间谱反演算法。利用山西省电力公司长治变电站110 kV高压变压器提取的油样(挂网运行年限分别为1, 10和20年), 进行检测装置性能的验证及测试。结果表明, 在17.173 MHz条件下, 该检测方法可以在1分钟内完成一次油样的信号检测与弛豫谱反演, 3种油样的弛豫时间峰值分别为203.83, 145.82和141.95 ms。可以看出, 随着年限的增加, 弛豫时间呈下降的趋势, 表明高温能够导致油品中分子化学键断裂, 析出气体。

Research on Transformer Oil Aging by Nuclear Magnetic ResonanceSpectroscopy of Relaxation Time

According to the limitations of conventional thermal aging detection of transformer oil insulation (notaccurate or complicated process), a low field nuclear magnetic resonance relaxation time spectrum detectionmethod is proposed. Based on the principle that hydrocarbon compounds in oil are cracked in high-pressuredischarge environment and the molecular structure of hydrogen-containing molecules is changed, a transverseNMR relaxation spectrum detection system for thermal aging of transformer oil is designed. An algorithm forobtaining relaxation time spectrum based on inversion is described by using the peak point of time domain signalof oil samples collected by spin echo sequence. With the oil samples from the 110 kV power station in ChangzhiCity, the aging factor was detected by the nuclear magnetic resonance relaxation spectroscopy. The oil sampleswere used for 1, 10 and 20 year, individually. The results show that, in a 17.173 MHz condition, the relaxation timeis 203.83, 145.82 and 141.95 ms, respectively. The detection time is controlled within 1 minute. The decreasingtrend of relaxation time indicates that the high temperature causes the breaking of molecular chemical bonds andthe precipitation of small hydrocarbon gases.