接地网磁激发极化效应及腐蚀诊断方法研究

Fault diagnosis and corrosion detection of grounding grid require excavation in the field. The non-excavation diagnosis and evaluation techniques are urgently need to be developed. During the research on defect diagnosis of grounding grid, the applicant noticed the magnetic induced polarization effect. In order to evaluate the corrosion status and locate the defect of grounding grid, we study the magnetic induced polarization mechanism of grounding grid, analyze the induced eddy current and polarization information. Combined with transient electromagnetic imaging method, we aim to evaluate the corrosion rate and degree, and locate the corrosion existing in grounding grid. This project plans to build the electrochemical model, electromagnetic induction model, induced polarization model based on the magnetic induced polarization of grounding grid, and grounding grid corrosion diagnosis model. This project investigate the magnetic polarization mechanism of grounding grid corrosion, the polarization response characteristics, the method to eliminate the polarization effect and eddy current effect, and the evaluation and diagnosis method of grounding grid corrosion. The transmitter-receiver instrument with optimal coupling, excitation source and receiving system will be developed. The corrosion diagnostic system will be built. This project develops linear polarization measurement probe with protect-loop technique and conducts comparative experiments between conventional electrochemical detection method and magnetic induced polarization method. This project crosses subjects of electrotechnology, geophysics and electrochemistry. Combined with the transient electromagnetic imaging method, it improves the practicability and operability of corrosion diagnosis of grounding grid. The similar studies have never been reported.

接地网缺陷诊断、腐蚀检测主要依赖于现场开挖，非开挖诊断与评价技术亟待取得突破。申请人在研究瞬变电磁的接地网缺陷诊断中，发现了接地网的磁激发极化现象。以解决接地网腐蚀状态评价与缺陷定位为目标，研究接地网的磁激发极化机理，解析接地网感应涡流和极化效应信息，与瞬变电磁成像法结合，实现接地网腐蚀速率、腐蚀程度评估和腐蚀定位：本项目拟建立磁激发极化的接地网腐蚀电化学模型、电磁感应模型和激发极化模型，接地网腐蚀诊断模型；研究接地网腐蚀磁极化机理，极化响应特征，极化效应和涡流效应的剥离方法，以及接地网腐蚀的评价与诊断技术；研制优化耦合的收发装置、激励源和接收系统，构建接地网腐蚀诊断系统；研制护环技术线性极化测量探头，开展常规电化学检测法与磁激发极化法对比实验。本项目是电工学科与地球物理、电化学学科的交叉，与瞬变电磁成像法结合，提高接地网腐蚀诊断的实用性、可操作性，而类似研究在国内外未见报道。

接地网腐蚀，泄流性能下降，给变电站人员和设备带来安全隐患，接地网缺陷诊断、腐蚀监测和状态评价十分重要。本项目提出了解析瞬变电磁法接地网感应涡流效应和极化效应信息，用于接地网腐蚀速率、腐蚀程度和腐蚀定位的新思路。同步开展了磁性源和电性源瞬变电磁法的接地网腐蚀诊断方法研究，电性源激发极化侧重于接地网整体腐蚀的诊断，磁性源瞬变电磁侧重于接地网腐蚀的局部定位。两者结合，使接地网状态评价方法更为完整。.开展了接地网腐蚀速率的影响因素研究，设计了腐蚀速率测量传感器，研制了三电极结构的检测仪器，建立了接地网加速腐蚀研究平台，开展常规腐蚀检测与强极化腐蚀检测对比，强极化衰减曲线的影响因素分析、建模仿真和加速腐蚀实验，电性源激发极化腐蚀评价模型，磁性源瞬变电磁接地网腐蚀检测及比对等工作。提出了多点旋转注入双极性陡脉冲电流，测量地表脉冲磁场感应电压，并根据磁场分布特征提取接地网拓扑结构的方法，研发了组合脉冲源电磁发射机、二分量磁场接收机，开发了小波边缘检测、形态滤波的拓扑结构成像算法。提出了自变量输入模式的神经网络求解视电阻率方法，通过ANN映射视电阻率，研究了混合多目标学习算法MEPDEN模型更为简洁高效。提出了接地网相对腐蚀度概念，腐蚀程度量化评价方法，用视电阻率成像对接地网进行快速扫描诊断，用聚类方法对接地网的腐蚀情况分类。设计了两种发射与接收一体式的检测装置，可实现对接地网二次场的精确测量，有效消除了一次场对测量结果的影响。提出了跨环消耦消一次场影响的一体化线圈结构，研究了在信号灵敏度、带宽、稳定性等方面的优缺点，并对线圈参数优化设计，研发了磁性源瞬变电磁接地网腐蚀检测系统。测试了20余个变电站，部分开挖，验证了磁性源瞬变电磁对地网拓扑和腐蚀检测可行性。电性源激发极化的电化学模型、电路模型更容易建立和评估，在此方向的拓展有望取得具有推广价值的成果。

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