Abstract
When the current distribution changes due to the breakage in the grounding grid, the magnetic field in the vicinity of the grounding grid will change, hence the magnetic field on the ground above the grounding can be used to detect the breakage of the grounding. In the paper, the magnetic field forward problem of the grounding grid is described firstly, and simulations were carried out when the breakage was located at different position. Results indicate that the maximum change of the magnetic flux density occurs at different measuring point when the breakage was located at different position. To achieve a more convenient method to detect the grounding grid fault, the magnetic field inverse problem of the grounding grid is presented, which is the process to calculate the current flowing in the grounding grid according to the magnetic field strength, and the method based on the global regularization and Damped Gauss-Newton method to solve the inverse problem is described, with which the ill-posed and ill-conditioning characteristic of the inverse problem can be diminished. Then the fault state of the grounding grid can be confirmed in the following way. Firstly, inject a 10∼30A current into the grounding grid, measure the magnetic field strength or the magnetic flux density at the measuring points on the ground above the grounding grid, then the current distribution can be obtained by solving the inverse problem. If the parameters of the soil are known, the resistance distribution can be obtained, with which the fault state of the grounding grid and the location of the fault can be confirmed. An equivalent model to verify the inverse problem was set up, and results indicate that the global regularization can diminish the ill-posed and ill-conditioning characteristic of the inverse problem.