Research On Breakpoint Detection Of Ground-electrode Network Based On Transient Electromagnetic Method

The grounding grids of substations play an important role in operationstabilityof power system and safety of operators.In China,the grounding grids are mainly made of flat and round steel materials,which is so easily corroded that it becomes thinner to crack.When the system has short-circuit faults or been struck by lightning,the fault currentcan't berapid discharged,which endangers the safety of equipment and people.Therefore,we study a method that isn't limited by the conditions of operating sites.Diagnosing breakpoints of grounding grids is a hot topic in grounding grids detection technology.The paper launches research on diagnosing breakpoints of grounding grids based on TEM,according to the principle of TEM anomaly loop,taking the grounding grids conductor as an abnormal coil horizontally placed side by side.The surficial emitting coil will cause the induced current in the grounding grids.We judge whether there is a breakpoint and its approximate location by the changes of induction voltage in receiving coil.The main research achievements of the paper are as follows.(1)We used the method of numerical calculation based on the theory of anomaly loop to simulate the induced voltage curves of the receiving coil when the grounding grid is in good condition and with different locations breakpoints.We compared these curve graphs to analyze the locations of breakpoints.(2)The paper introduced the BP neural network method.It used the voltage value of of indoor experiments with simulation results verifies the effectiveness of the method.different locations breakpoints by simulation calculation,taking the value as the input of neural network and the position as the output.After training,it can automatically diagnose breakpoints through the trained neural network.(3)I built a PCA-BP neural network according to the method that combines principal component analysis(PCA)with BP neural network.I also made the principal component extraction of input sample and reduced its dimension,which simplifies the network and enhances the efficiency of the diagnosis.(4)Comparing the results of indoor experiments with simulation results verifies the effectiveness of the method.(5)I designed the diagnosing interface of grounding grids breakpoints by using MATLAB GUI.Testing the network with actual measured data proves the accuracy of the designed network.It doesn't need to rely on grounding grids wires with the method of TEM for detecting ground grids breakpoints,which has high operability and provides an easy method of effective detection.