Study On Characteristics Of Non-uniform Soil Resistivity Near Grounding Device

The grounding grid plays a significant role in maintaining the safe operation of power system.The grounding resistance is affected by many factors,such as the grounding device,soil resistivity distribution,and other factors.Compared with the grounding grid of substation,the grounding range of the pole tower is smaller.And the distribution of local resistivity in shallow soil has a greater impact on the leakage of the grounding device.However,the design and construction of grounding grids are usually carried out in accordance with the uniform distribution of soil due to lack of the real condition of soil structure.When the resistivity near the grounding device is higher than the resistivity assumed in advance,the grounding resistance is greater than the design value.Based on the above research background,in order to find out the soil structure in the early stage of construction,the main contents of the paper are as follows:(1)Based on the basic principle of the direct current method,the law of direct current flow in the underground half-space was investigated.Based on the finite difference method,and the distribution of the potential in the space is simulated using MATLAB with the encrypted grid in the shallow layer.In order to make the measurement data containing more information about the underground resistivity distribution,an unequal depth distribution mode of the measuring electrode and the excitation electrode is proposed to change the current flow path.The results show that in this electrode arrangement mode,the measurement data contains more electrical information.(2)Based on the unequal depth arrangement of electrodes,a 2.5-dimensional resistivity forward program was written.Compared with the commen results of forward,it was found that this imaging algorithm have a higher sensitive of low-resistance abnormal objects distribution.A variety of common geoelectric body models are established to explore the influence of the distribution of anomalous bodies on the apparent resistivity map.And the real resistivity distribution of the underground half space is explained using the measured apparent resistivity distribution map.(3)Based on the anomaly detection theory,various factors affecting the detection effect are analyzed.The maximum detectable depth was selected as the evaluation index to evaluate the detection effectiveness.Multiple factors such as the selected electrode spacing,the buried depth of the abnormal body,and the radius of the abnormal body on the detection were investigated respectively.The results show that the selected electrode distance has the greatest influence on the detection imaging results.The limitations of the high-density electrical method are analyzed.Based on the different resistivity distributions,suggestions for the best detection scheme are provided.(4)A water tank simulation experiment platform was built,and the physical simulation of the forward algorithm proposed in this paper was verified.The resistivity of the liquid in the water tank is changed by adding solutes to the water.Objects with different resistivity are used to simulate the distribution of various resistivities in the actual engineering environment.The experimental and simulation results show that the algorithm proposed in this paper can obviously solve the distribution of anomalous bodies.