接地网故障诊断的磁场逆问题求解方法

变电站接地网是变电站安全运行的保障，接地网出现故障会严重威胁站内人员和设备的安全。笔者提出了基于磁场逆问题的接地网诊断方法，通过向接地网两根上引导体注入和抽出低频电流，在接地网地表产生磁场，从而建立磁场逆问题方程，采用正则化方法对逆问题的病态性进行处理，采用牛顿迭代法对逆问题进行求解，得出接地网各个回路的电流分布，进而分析其电阻变化，判断接地网的腐蚀状态。以一个4×4接地网为例，建立了其磁场逆问题方程，利用正则化的方法对逆问题进行求解，将计算结果与正问题结果相比，误差控制在3%以内，验证了所提出逆问题的求解方法。讨论了测量点数量的选择，指出测量点数量选取为网孔数的40%即可较好地近似真实磁场分布。

Computation method of magnetic field inverse problem on grounding grids fault diagnosis

Grounding grids are the guarantee of substation running safety. The fault of grounding grids is a threat to people and equipment in substations. A method to diagnose the fault of grounding grids based on magnetic field inverse problem. The inverse problem of magnetic field is established by injecting and extracting a low frequency current. The morbid of inverse problem is solved through regularization and Newton iteration method to obtain the distribution of the mesh currents. The approximate distribution of the magnetic field is calculated to diagnose the fault of the grounding grid. A 4×4 substation grounding grids is taken as an example. By comparison of the forward problem result, the error is under 3%, so the prposed method of inverse problem is verified. The selection of measurement point is discussed, and 40% of the number of meshes is accounted to approximate the real distribution of the magnetic field on the grounding grids.