An earth potential discrete solving method for stray current spatial propagation analysis

Abstract

The present application relates to a kind of ground potential discrete solving method for stray current space propagation analysis, including zoning profile according to the stratum space of study area, and in the region where current injection is strong, finer spatial division scale is used, in the part far from the region of interest, coarser division scale is used, to give consideration to calculation accuracy and solving efficiency;Stray current source is equivalently distributed to adjacent discrete unit node, and overall potential solving equation is established based on the conductive relationship between nodes;By numerically solving global discrete equation, the potential distribution and risk influence result of ground surface and the periphery of target facility are obtained.Compared with prior art, the present application can effectively reduce the calculation amount of large-scale space solving under the premise of maintaining high calculation accuracy, and is suitable for scenarios such as rail transit stray current intrusion, grounding grid potential analysis and transformer dc magnetic bias evaluation.

Description

Technical Field

[0001] This invention relates to the field of ground potential modeling and numerical analysis, and in particular to a method for discretely solving ground potential for analysis of stray current spatial propagation. Background Technology

[0002] With the continuous expansion of urban rail transit systems, power grounding systems, and underground metal facilities, the problem of leakage current propagation in underground spaces has gradually attracted attention. During rail transit operation, some traction return current will break through the ideal constraints of the rails and return system, and diffuse into the surrounding area through the soil medium, grounding structure, and buried metal conductors, thereby changing the original potential distribution state of the underground space and forming a complex ground potential field.

[0003] When a continuous leakage current exists in an underground space, a potential difference will be generated between different areas, thus forming a ground potential gradient. This type of ground potential change not only leads to corrosion of underground metal facilities but also causes problems such as local potential rise in the grounding grid and potential shift at the neutral point of the main transformer. Therefore, accurately calculating the distribution and variation patterns of ground potential in underground spaces has become a key issue in stray current analysis, grounding safety assessment, and DC bias magnetization research in rail transit.

[0004] Existing methods for calculating ground potential typically employ lumped parameter network models, homogeneous medium analytical models, or three-dimensional mesh models. Lumped parameter models often treat the underground space as a series of discrete grounding resistance units, which, while simpler in calculation, struggles to describe continuous potential changes within the underground space. Homogeneous medium analytical models are usually based on the assumption of ideal homogeneous soil, making it difficult to reflect the impact of soil parameter variations, underground structure distribution, and complex boundary conditions on ground potential propagation. While three-dimensional mesh models can improve spatial description capabilities to some extent, in large-scale underground region analysis, using uniform fine-scale discretization leads to a sharp increase in the number of computational nodes, resulting in decreased solution efficiency; conversely, using uniform coarse-scale discretization makes it difficult to accurately describe the local potential change characteristics of key areas.

[0005] Furthermore, in actual underground spaces, leakage currents are typically characterized by dispersed locations, complex propagation paths, and significant local concentrations, resulting in substantial differences in potential variation across different areas. Traditional modeling methods struggle to balance computational accuracy in local areas with overall solution efficiency, thus limiting the application of ground potential calculations in substation grounding system analysis and DC bias risk assessment of main transformers.

[0006] Chinese invention patent CN112883597A discloses a method for calculating the DC biased ground potential of transformers caused by stray currents in subways. This invention utilizes finite element analysis to mesh a three-dimensional earth resistivity model, calculates the ground potential, and outputs the calculation results through a post-processing module. Based on earth and power grid data, it can predict transformers that may experience biased magnetization. Using this invention can reduce blind measurements and provide computational analysis tools for developing mitigation solutions. However, it still suffers from accuracy loss due to a uniform coarse mesh and numerical abrupt changes during the discretization process.

[0007] In summary, there is currently a lack of a discrete solution method for ground potential in the analysis of stray current spatial propagation, which can solve or partially solve the above problems. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the existing technology by providing a ground potential discretization solution method for stray current spatial propagation analysis, so as to solve or partially solve the problems of accuracy loss caused by uniform coarse grid and numerical mutation during the discretization process.

[0009] The objective of this invention can be achieved through the following technical solutions: According to one aspect of the present invention, a method for discretizing ground potential for stray current spatial propagation analysis is provided, comprising: S1. Based on the importance of the region, different spatial discrete scales are set to divide the underground conductive space of the target region into layers and set discrete nodes; S2. For the stray current injection region, the current source is mapped to adjacent discrete nodes in a spatial distribution manner; S3. Construct a global potential solution equation based on the conduction relationship between the discrete nodes; S4. Solve the global potential equation to obtain the potential gradient distribution of the surface and subsurface space of the target area; S5. Based on the potential gradient distribution, determine the main propagation path, diffusion range, and coupling effect of stray current in the substation grounding grid area, and analyze the risk of neutral point offset and DC bias of the main transformer based on the judgment results.

[0010] As a preferred technical solution, the result obtained by the hierarchical partitioning includes a key analysis area, a region far from the key analysis area, and a transition area. The key analysis area is partitioned using a spatial partitioning with a thickness less than a preset value, the region far from the key analysis area is partitioned using a spatial partitioning with a thickness greater than a preset value, and the transition area is used to connect the key analysis area and the region far from the key analysis area.

[0011] As a preferred technical solution, the key analysis area includes areas with concentrated current injection, significant structural changes, or close relationship with the target device.

[0012] As a preferred technical solution, mapping the current source to adjacent discrete nodes in a spatial allocation manner includes: Determine the spatial location of the current source; Select several neighboring discrete nodes that surround the spatial location; The allocation coefficients are calculated based on the spatial location and the relative geometric relationship between each neighboring discrete node; The current injection amount is allocated to the neighboring discrete nodes according to the allocation coefficient.

[0013] As a preferred technical solution, the allocation coefficient satisfies the normalization constraint.

[0014] As a preferred technical solution, the conductivity relationship between the discrete nodes is determined by the soil medium parameters, the interlayer connection relationship, and the equivalent channel of the buried conductor.

[0015] As a preferred technical solution, the step of obtaining the node potential distribution includes: performing numerical calculations on the global potential solution equation to obtain the potential results of each node in the region, and calculating the potential gradient distribution of the surface and underground space based on the potential results.

[0016] As a preferred technical solution, the global potential solution equation is established based on the equivalent conduction relationship between discrete nodes, which includes longitudinal conduction components, lateral conduction components, and interlayer coupling components.

[0017] As a preferred technical solution, the method also includes quantitatively assessing the risk of DC bias by combining indicators such as the change in transformer neutral point potential, the current flowing into the grounding grid, and the distortion of the excitation waveform.

[0018] According to another aspect of the present invention, a ground potential discretization solution system for stray current spatial propagation analysis is provided, the system being used to perform the ground potential discretization solution method for stray current spatial propagation analysis as described above, the system comprising: The layered segmentation module is used to perform layered segmentation of the underground conductive space of the target area, including the key analysis area, the area away from the key analysis area, and the transition zone. The mapping module is used to map current sources to adjacent discrete nodes in a spatial allocation manner for stray current injection regions. The solution module is used to construct a global potential solution equation based on the conductive connections between the discrete nodes, and solve for the node potential distribution in the target region. The output module is used to determine the main propagation path, diffusion range, and coupling effect of stray current in the substation grounding grid area based on the node potential distribution, and to analyze and output the neutral point offset and DC bias risk of the main transformer based on the judgment results.

[0019] Compared with the prior art, the present invention has at least one of the following beneficial effects: (1) This invention divides the underground conductive space of the target area into layers and sets different spatial discrete scales according to the importance of the area, so that the local potential changes in the key area can be more finely characterized. This solves the problem of accuracy loss caused by uniform coarse grid, and achieves the technical effect of accurately describing the local potential change characteristics of the key area and increasing the solution efficiency.

[0020] (2) The present invention calculates the allocation coefficient by means of the spatial position and the relative geometric relationship between each neighboring discrete node, and then allocates the current injection amount to the neighboring discrete nodes according to the allocation coefficient, which solves the problem of numerical mutation in the discretization process and achieves a smoother and more stable technical effect in solving the node potential.

[0021] (3) This invention combines the refinement of key areas with the coarsening of far-field areas, which significantly reduces the overall computational scale while ensuring the analysis accuracy of key areas, and is suitable for modeling large-scale underground conductive spaces. This invention can be directly used for stray current intrusion analysis of substations around rail transit, grounding grid potential assessment, and transformer DC bias risk prediction, and has strong engineering applicability. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall process of the method of the present invention; Figure 2 This is a schematic diagram of the unevenly partitioned underground space structure and the spatial distribution of stray current sources in this invention. Figure 3 This is a schematic diagram of the process for numerically solving the node potential in this invention; Figure 4 This is a schematic diagram of the propagation path and risk assessment process based on node potential in this invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0024] Example 1 To address the problems existing in the prior art, this embodiment provides a method for discretizing and solving ground potential for stray current spatial propagation analysis, such as... Figure 1 As shown, it specifically includes: S1. The underground conductive space of the target area is divided into layers, and different spatial discrete scales are set according to the importance of the area.

[0025] Specifically, the target area is spatially partitioned based on the spatial range of the research object, the distribution of underground media, and the range of current influence, and different discrete step lengths are set according to the importance of different areas. For areas with concentrated current injection, significant structural changes, or close relationship with the target equipment, a finer spatial partition is used; for areas far from the focus of analysis, a relatively coarse spatial partition is used to form a layered spatial calculation structure.

[0026] Spatial partitioning includes at least three levels: a core analysis zone, a transition buffer zone, and a distant background zone. The core analysis zone, i.e., the area of ​​focus for analysis, uses the minimum step size; the transition buffer zone uses a medium step size; and the distant background zone, i.e., far from the focus area, uses a larger step size, thus preserving higher spatial resolution in critical areas. The core zone includes areas surrounding rail transit lines, areas near grounding grids, areas adjacent to transformers, or areas with dense buried metal structures. For example... Figure 2 As shown, Figure 2 The diagram shows the non-uniformly partitioned structure of the underground space and the spatial distribution of stray current sources.

[0027] S2. For stray current injection regions, the current sources are mapped to adjacent discrete nodes in a spatial distribution manner.

[0028] Specifically, the location of the stray current source is mapped to several discrete nodes around it to determine the spatial location of the current source. Based on the relative geometric relationship between this spatial location and each neighboring discrete node, the corresponding allocation coefficient is calculated, thereby smoothly applying the current injection amount to the neighboring discrete nodes and avoiding numerical abrupt changes caused by current in a single node. The allocation coefficients satisfy the normalization constraint, that is, the sum of all allocation coefficients equals 1.

[0029] The current source mapping process adopts a multi-node allocation method based on spatial weights. The spatial weights are determined by the distance relationship between the current source location and surrounding nodes, as well as the geometric relationship of the elements.

[0030] S3. Construct a global potential solution equation based on the conductive connection between discrete nodes, where the conductive relationship between nodes is determined by soil medium parameters, interlayer connection relationship, and equivalent channel of buried conductor.

[0031] The global solution model is expressed in a sparse form to reduce memory usage and improve the solution speed of large-scale discrete systems. The global potential solution equation is established based on the equivalent conduction relationship between discrete nodes, which includes longitudinal conduction components, lateral conduction components, and inter-layer coupling components.

[0032] S4. Solve the global potential equation to obtain the node potential distribution in the target region.

[0033] The solution process is as follows Figure 3 As shown, specifically, the numerical calculation employs one or more combinations of sparse matrix solving, iterative methods, or direct methods to obtain the potential results of each node within the region. Based on these results, the potential gradient distribution of the surface and subsurface spaces is calculated. The node potential distribution is used to determine the main propagation path of stray currents and to calculate the potential gradient within the target region.

[0034] S5. Based on the node potential distribution, determine the main propagation path, diffusion range, and coupling effect of stray current in the substation grounding grid area, and analyze the risk of neutral point offset and DC bias of the main transformer based on the judgment results.

[0035] The method of the present invention can also combine indicators such as the change of transformer neutral point potential, grounding grid inflow current and excitation waveform distortion to quantitatively assess the risk of DC bias.

[0036] In this embodiment, a 220 kV substation near a city rail line is taken as the research object. An underground conductive space model is established, including the rail line, the surrounding soil area, and the substation grounding grid. The research area can be a three-dimensional space with a length of 1000 meters, a width of 500 meters, and a depth of 60 meters. The rail line is located in the central part of the research area, and the substation is located within approximately 150 to 250 meters to one side of the rail line. For the stratigraphic structure, it can be set as a three-layer or multi-layer structure according to the actual geological survey data. For example: the surface backfill layer is 0 to 2 meters thick with a resistivity of 20 to 40 (Ω·m); the intermediate clay layer is 2 to 15 meters thick with a resistivity of 50 to 120 (Ω·m); and the lower sandstone or deeper soil layer is less than 15 meters thick with a resistivity of 100 to 300 (Ω·m). The parameters of each layer can be corrected according to the field measurement data.

[0037] When spatially discretized, the study area is divided into three parts: a core analysis area, a transition area, and a background area. The core analysis area, i.e., the key analysis region, is used to characterize the vicinity of the track line, the substation grounding grid, areas with dense buried metal structures, and the area associated with the main transformer. The core analysis area is preferably set within a range of 0 to 50 meters from the track centerline and 0 to 80 meters from the substation perimeter wall. A finer discretization step size is used in this area to improve the ability to capture local potential abrupt changes and current convergence paths. Preferably, the horizontal discretization step size is 0.5 to 1 meter, and the vertical discretization step size is 0.25 to 0.5 meters.

[0038] The background area, i.e., the area far from the focus of analysis, is used to characterize the vast underground space far from the focus of analysis, mainly to provide the boundaries for current return and potential decay. This area can preferably be set at a distance of more than 180 meters from the center of the track or substation, with a horizontal distance of 5 to 20 meters and a vertical distance of 2 to 5 meters from the walkway.

[0039] The transition zone connects the core analysis area and the background area, primarily to mitigate mesh size variations and prevent computational error concentration. This zone is preferably set between 50 and 180 meters from the outer edge of the core analysis area, with a horizontal distance of 2 to 5 meters from the walk distance and a vertical distance of 1 to 2 meters from the walk distance.

[0040] After spatial partitioning, stray current sources are mapped to adjacent discrete nodes according to their actual locations. The current source is not directly applied to a single node; instead, the injected current is distributed to the eight corner nodes based on its relative position within the cell. This reduces local numerical abrupt changes caused by single-point injection and better reflects the actual spatial propagation process. Suppose a stray current source is located inside a 3D mesh cell, and its normalized position relative to the lower left front corner of the cell along three directions is as follows: the position ratio in the first direction is a value between 0 and 1; the position ratio in the second direction is a value between 0 and 1; and the position ratio in the third direction is a value between 0 and 1. For example, when the total current of a stray current source is 10 amperes, and its position ratios within the cell are 0.2, 0.6, and 0.4, the eight corner nodes receive different weights of injected current, with larger currents received closer to the source and smaller currents received farther away. This method makes the source term representation smoother. If the stray current source is located at the cell boundary or node, it can be further simplified to be distributed according to two or four adjacent nodes, and the distribution rule can be automatically degraded according to the actual geometric position.

[0041] After spatial discretization and current mapping, the equivalent conduction relationship between nodes is established based on the soil resistivity, upper and lower layer connections, and buried conductor channels of each discrete unit. For any two adjacent nodes, the equivalent conduction value between the nodes can be calculated according to Ohm's law and geometric relationships.

[0042] If the distance between two adjacent nodes is the grid step size in a certain direction, and the cross-sectional area of ​​the channel between the two nodes is the cell cross-sectional area in that direction, then the equivalent conduction value between the two nodes can be expressed as g = A / ρl, where g represents the equivalent conduction value between adjacent nodes, in Siemens; A represents the current flow cross-sectional area, in square meters; ρ represents the soil resistivity of the region, in ohm-meters; and l represents the distance between the two nodes, in meters. Furthermore, for any node, its current balance equation can be expressed as: the sum of the currents flowing out of the node to each adjacent node, minus the current injected into the node, equals zero. By simultaneously solving the current balance equations for all nodes, the global potential equation can be obtained: GV=I Where G represents the global conductivity matrix; V represents the column vector composed of the potentials of each discrete node; and I represents the column vector composed of the injected currents of each node. In the matrix, the diagonal elements represent the sum of the conduction values ​​of the node and all its adjacent nodes; the off-diagonal elements represent the negative values ​​of the conduction values ​​between two adjacent nodes. In other words, if a node has conduction relationships with adjacent nodes in each of the six directions, then the diagonal element corresponding to that node is the sum of the six conduction values, while the corresponding elements of other nodes directly connected to it take the opposite value. To ensure the uniqueness of the reference potential, a node far from the boundary of the study area can be selected as the zero-potential reference point, or certain boundary nodes in the far background area can be uniformly set as zero-potential boundaries. For this embodiment, the boundary surface farthest from the track and substation can be set as the zero-potential boundary to simulate far-field potential attenuation.

[0043] After obtaining the potential of each node, the potential difference and spatial potential gradient between adjacent nodes are further calculated to identify the main diffusion paths and accumulation regions of stray currents. Since current always propagates in the direction of decreasing potential, the possible flow direction of the current can be deduced from the changes in potential.

[0044] If the potentials of a node in the three directions of left, right, front, back, up, and down are respectively the potentials of its adjacent nodes, then its spatial potential gradient can be approximated by the following formula: in, V 右 , V 左 These represent the potentials of the nodes adjacent to the right and left of this node, respectively; V 后 , V 前 These represent the potentials of adjacent nodes on the rear and front sides, respectively; V 上 , V 下Δx, Δy, and Δz represent the potentials of adjacent nodes on the upper and lower sides, respectively; Δx, Δy, and Δz represent the grid step sizes in the three directions. If the potential gradient increases significantly in a certain area, it indicates that the current convergence or divergence is strong at that location, and the current propagation path can be further identified by combining the potential contour map. For the core analysis area, the peak location of the potential gradient can also be statistically analyzed as a priority area for judging stray current intrusion into the grounding grid.

[0045] To ensure the uniqueness of the reference potential, a node far from the boundary of the study area can be selected as the zero-potential reference point, or certain boundary nodes in the distant background area can be uniformly set as zero-potential boundaries. In this embodiment, the boundary surface farthest from the track and substation can be set as the zero-potential boundary to simulate far-field potential attenuation.

[0046] After obtaining the potential distribution of each discrete node in the underground space, a grounding response analysis can be further performed on the substation area to assess the impact of stray currents on the grounding system and the neutral point of the main transformer. For example... Figure 4 As shown, in this embodiment, the node potential of the area where the substation grounding grid is located is first extracted. Since the grounding grid is usually composed of multiple horizontal grounding conductors and vertical grounding electrodes, multiple discrete nodes in the corresponding area of ​​the grounding grid can be regarded as grounding system associated nodes. By statistically analyzing the potential distribution of each associated node, the overall potential rise of the grounding grid can be obtained. When stray track currents diffuse towards the substation through underground space, local potential rise usually occurs near the substation grounding grid. If there is a significant potential difference between different areas of the grounding grid, it indicates that stray currents may have formed a spatial flow path within the grounding system. Further, equivalent nodes are extracted for the neutral point connection area of ​​the main transformer. Since the neutral point of the main transformer is usually connected to the grounding grid through a grounding down conductor, the discrete node potentials corresponding to the neutral point connection location can be used as the equivalent potential of the neutral point. Further, based on the equivalent conduction relationship of the neutral point grounding branch, the DC current component flowing into the neutral point of the main transformer can be calculated. The neutral point DC current can be expressed as: I 中性点 =(U 中性点 -U 接地网 ) / R 接地支路 Furthermore, the risk of DC bias in the main transformer can be graded and assessed based on the magnitude of the DC current flowing into the neutral point. Since DC current entering the transformer windings causes a shift in the core flux, leading to excitation current distortion, increased local vibration, and higher harmonic content, the neutral point DC current can be used as an important criterion for assessing bias risk. Risk is classified as follows: a neutral point DC current less than 1 ampere is considered low-risk; a neutral point DC current between 1 and 2 amperes is considered moderate-risk; a neutral point DC current between 2 and 5 amperes is considered relatively high-risk; and a neutral point DC current greater than 5 amperes is considered high-risk. It should be noted that the above risk thresholds can be adjusted according to the transformer voltage level, capacity, neutral point grounding method, and operating standards.

[0047] Furthermore, by analyzing the potential gradient direction within the grounding grid area, the main convergence path of stray currents entering the grounding system can be identified. For example, when the potential at the edge of the grounding grid is significantly higher than that in the central area, it indicates that stray currents may preferentially enter from the outer conductor of the grounding grid and propagate along the grounding conductor towards the neutral point of the main transformer.

[0048] This invention combines the results of underground space potential calculation with the response of substation grounding system, enabling a continuous analysis process from stray current spatial diffusion to the risk of main transformer bias magnetization, thereby providing a basis for risk assessment, protection design, and operation monitoring of substations around urban rail transit.

[0049] Example 2 Regarding the ground potential discretization solution method for stray current spatial propagation analysis provided in the foregoing embodiments, this embodiment provides a ground potential discretization solution system for stray current spatial propagation analysis, used to execute the aforementioned ground potential discretization solution method for stray current spatial propagation analysis, specifically including: The layered segmentation module is used to perform layered segmentation of the underground conductive space of the target area, including the key analysis area, the area away from the key analysis area, and the transition zone. The mapping module is used to map current sources to adjacent discrete nodes in a spatial allocation manner for stray current injection regions. The solver module is used to construct a global potential solution equation based on the conductive connections between discrete nodes, and solve for the node potential distribution in the target region. The output module is used to determine the main propagation path, diffusion range, and coupling effect of stray current in the substation grounding grid area based on the node potential distribution. Based on the judgment results, it analyzes and outputs the risk of neutral point offset and DC bias of the main transformer.

[0050] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for solving the surface potential problem of the ground potential discrete method for the analysis of the spatial propagation of the stray current, characterized in that, The method includes: S1. Based on the importance of the region, different spatial discrete scales are set to divide the underground conductive space of the target region into layers and set discrete nodes; S2. For the stray current injection region, the current source is mapped to adjacent discrete nodes in a spatial distribution manner; S3. Construct a global potential solution equation based on the conduction relationship between the discrete nodes; S4. Solve the global potential equation to obtain the potential gradient distribution of the surface and subsurface space of the target area; S5. Based on the potential gradient distribution, determine the main propagation path, diffusion range, and coupling effect of stray current in the substation grounding grid area, and analyze the risk of neutral point offset and DC bias of the main transformer based on the judgment results.

2. The method of claim 1, wherein, The result obtained by the hierarchical partitioning includes a key analysis area, a region far from the key analysis area, and a transition area. The key analysis area is partitioned using a spatial partitioning with a thickness less than a preset value, while the region far from the key analysis area is partitioned using a spatial partitioning with a thickness greater than a preset value. The transition area is used to connect the key analysis area and the region far from the key analysis area.

3. The method of claim 2, wherein, The key areas of analysis include regions with concentrated current injection, significant structural changes, or those closely related to the target device.

4. The ground potential discretization solution method for stray current spatial propagation analysis according to claim 1, characterized in that, The step of mapping the current source to adjacent discrete nodes in a spatial allocation manner includes: Determine the spatial location of the current source; Select several neighboring discrete nodes that surround the spatial location; The allocation coefficients are calculated based on the spatial location and the relative geometric relationship between each neighboring discrete node; The current injection amount is allocated to the neighboring discrete nodes according to the allocation coefficient.

5. The ground potential discretization solution method for stray current spatial propagation analysis according to claim 4, characterized in that, The allocation coefficients satisfy the normalization constraint.

6. The ground potential discretization solution method for stray current spatial propagation analysis according to claim 1, characterized in that, The conductivity between the discrete nodes is determined by the soil medium parameters, the interlayer connection, and the equivalent channel of the buried conductor.

7. The ground potential discretization solution method for stray current spatial propagation analysis according to claim 1, characterized in that, The steps for obtaining the potential gradient distribution of the surface and underground space include: performing numerical calculations on the global potential solution equation to obtain the potential results of each node in the region, and calculating the potential gradient distribution of the surface and underground space based on the potential results.

8. The ground potential discretization solution method for stray current spatial propagation analysis according to claim 1, characterized in that, The global potential solution equation is established based on the equivalent conduction relationship between discrete nodes, which includes longitudinal conduction components, lateral conduction components, and interlayer coupling components.

9. The ground potential discretization solution method for stray current spatial propagation analysis according to claim 1, characterized in that, The method also includes quantitatively assessing the risk of DC bias by combining indicators such as changes in transformer neutral point potential, grounding grid inflow current, and excitation waveform distortion.

10. A discrete solution system for ground potential analysis of stray current spatial propagation, characterized in that, The system is used to execute the ground potential discretization solution method for stray current spatial propagation analysis as described in any one of claims 1-9, and the system includes: The layered segmentation module is used to perform layered segmentation of the underground conductive space of the target area, including the key analysis area, the area away from the key analysis area, and the transition zone. The mapping module is used to map current sources to adjacent discrete nodes in a spatial allocation manner for stray current injection regions. The solution module is used to construct a global potential solution equation based on the conductive connection between the discrete nodes, and solve for the potential gradient distribution of the surface and underground space of the target area. The output module is used to determine the main propagation path, diffusion range, and coupling effect of stray current in the substation grounding grid area based on the node potential distribution, and to analyze and output the neutral point offset and DC bias risk of the main transformer based on the judgment results.

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