瞬变电磁法电阻率成像的接地网故障诊断基础研究

The fault of grounding grid is an important factor to affect the Stability and safety operation of power system .Digging test, as a method applied widely, which is aimless and difficult to find the fault, influences the operation of system and causes economic losses . Researching on recognize and orientate the breaks or corrosion sites correctly without digging is a trend in the field. Because the new methods proposed in current, such as the electric network method, are imperfect and limited. So, practical and effective diagnosis methods and technology need to be further researched..This project will research the mechanism of transient electromagnetic construction and diffusion in grounding grid, the optimization device of the transmitter and receiver, the correction of transient process, the separation between the primary and secondary filed, the wavelet de-noising technology and net secondary field detection with three component, 2D imaging of induced voltage, 3D imaging of the apparent resistivity and shallow apparent resistivity correction method considering the displacement current effects. A systematic TEM method applied in the area of grounding will be bulit..We will also research how the grounding grid conductor material, the extent of corrosion, soil electromagnetic properties, the geometric size of the grounding grid and the grid distribution, as well as different fault conditions influence the response characteristics abnormalities of TEM and the abnormalities of apparent resistivity. We will propose a pattern recognition method to diagnosis breaks and corrosion points of grounding grids by means of the 3D imaging of the induced voltage and apparent resistivity..This project is the intersection of EE and geophysics, therefore, it has significant innovative and broad prospects.

接地网故障是影响电力系统安全的重要因素，抽样开挖不能准确判断腐蚀程度和断点，停电检修会带来经济损失，电网络法等手段尚不成熟，因此，免停机的接地网缺陷免开挖诊断技术是未来的发展方向。. 研究接地网瞬变电磁建场和扩散机理，根据接地网导体大小、埋深和特有的网状结构，研究优化耦合的收发装置、激励源和接收系统。研究关断沿和过渡过程校正，一次场和二次场分离和小波去噪技术，实现三分量净二次场检测。研究感应电压平面图成像、视电阻率三维成像及考虑位移电流影响的校正方法，形成较为系统的接地网瞬变电磁法。. 研究接地网导体材料、腐蚀程度、土壤电磁特性、接地网几何尺寸和网格分布，以及不同故障情况的瞬变电磁响应特征及视电阻率异常表现，借助于感应电压成像和视电阻率三维成像，提出模式识别的非接触的免开挖接地网故障诊断新方法。. 本项目是本学科与地球物理学科的交叉，具有显著开创性和应用价值。

接地网腐蚀导致电力设施停运的事故屡见不鲜，对电力系统安全运行造成严重隐患。当前的接地网故障诊断普遍存在施工困难和实用性差的缺点，难以实现腐蚀程度的量化评价。课题提出了瞬变电磁法的研究路线，取得以下成果：.1）接地网瞬变电磁建模。研究了瞬变电磁理论，频域电磁法到时域的转换，瞬变电磁建模与数值计算方法，基于Maxwell建立了接地网三维正演模型，研究了接地网瞬变电磁特征，管线、测线布置方式对腐蚀诊断的影响。.2）接地网瞬变电磁装置模式研究。开展了小回线和大定源回线，Z分量和三分量，单磁探头和阵列型探头，磁性源和电性源的多种装置模式的比较分析，研究发送与接收回线最佳参数，设计优化的接地网瞬变电磁装置。.3）瞬变电磁早期信号处理技术。建立了接收线圈模型，分析了一次场、二次场特征，开展了过渡过程校正研究。研究了早期信号去噪的数据处理技术。研制了瞬变电磁发送接收一体化装置。.4）瞬变电磁视电阻率快速成像。开展了线性加速视电阻率数值计算方法、BP神经网络的瞬变电磁快速成像方法研究。.5）高速关断激励源。开展了单极性高速关断电流脉冲发射技术研究，研制了高精度恒流陡脉冲场源。.6）实验研究。开展了与GDP32电磁法系统和高密度电法仪的对比测试，验证了研制的瞬变电磁法系统的探测精细程度和准确性。在武汉南瑞、重庆电科院、重庆大学建立了接地网故障模拟试验场，成功判断了接地网扁钢的粗细差异和断点差异，提出了腐蚀率这一参数并得到成功验证。在宁夏、浙江、四川和重庆10余个变电站开展工况下地网腐蚀检测，证实接地网拓扑检测与实际一致，也反映了一些疑似腐蚀故障点。.课题证实瞬变电磁法确实能够反映接地网导体的腐蚀程度，并能够实现腐蚀程度的量化检测，这是该领域研究的重大突破。研究成果经进一步完善和细化，有望得到实际推广应用。研究成果已得到国家电网高度重视，已获总部课题进一步支持，并被推荐为2017年国网运检部推广项目。