Power station grounding grid fault current dispersion calculation method and system based on joint modeling

Abstract

The invention provides a power station grounding grid fault diffusion calculation method and system based on joint modeling, and belongs to the technical field of power protection. Comprising the following steps: constructing a joint model of layered soil and a conductor network based on soil layering parameters and grounding grid conductor network parameters; calculating the joint model by adopting a mixed numerical algorithm so as to determine the fault scattered current distribution of the grounding grid; and calculating electrical safety parameters of the grounding grid and adjusting a topological structure and a material of the grounding grid based on the distribution condition of the fault dispersed current. According to the method, the fault scattered current of the grounding grid of the power station in different fault scenes can be accurately calculated, so that effective safety guidance suggestions are provided for construction and maintenance of the grounding grid.

Description

Technical Field

[0001] This invention belongs to the field of power protection technology, and in particular relates to a method and system for calculating fault current dissipation in power plant grounding grids based on joint modeling. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] The power plant grounding grid is a critical facility for ensuring the safe and stable operation of the power system and protecting the safety of personnel and equipment. When a grounding fault occurs at a power plant, a huge fault current will dissipate into the surrounding soil through the grounding grid conductors. At this time, accurately calculating the fault current distribution of the grounding grid is the basis for assessing its key safety parameters such as grounding resistance, step voltage, and contact voltage, and is crucial for preventing electric shock accidents, avoiding localized overheating, and preventing equipment damage.

[0004] However, existing methods for calculating fault current dissipation in grounding grids have significant shortcomings, leading to large discrepancies between the calculated results and actual conditions, making it difficult to provide reliable safety guidance. These deficiencies are mainly reflected in the following two aspects: First, existing methods oversimplify the modeling of the grounding grid conductor network, neglecting its impedance distribution characteristics as a complex network. For example, current methods typically treat the grounding grid as an equipotential body or use the assumption of homogeneous conductors for analysis, failing to fully consider the profound impact of the conductor's own resistance and inductance, as well as the network structure formed by the interconnections between conductors, on the current dissipation path. This simplified model cannot reflect the actual axial flow and leakage patterns of fault current in the grounding grid, leading to deviations in the prediction of current dissipation hotspots and potential distribution, thus making the subsequent step voltage and contact voltage assessment results unreliable.

[0005] Secondly, existing methods generally employ a single, homogeneous soil model, failing to adequately consider the non-uniform influence of the actual soil's layered structure on current dissipation characteristics. In practical engineering, soil often has a layered structure, with significant differences in resistivity between layers. Existing calculation methods treat the soil as a homogeneous whole, neglecting the guiding, blocking, and distortion effects of high- or low-resistivity layers on the current dissipation path. Especially in scenarios with high-resistivity surface layers (such as gravel) or hard underground rock layers, this assumption of a single soil model can introduce significant errors, severely underestimating or overestimating the dangerous potential at the surface, posing potential risks to the safe operation of substations. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, this invention provides a method and system for calculating fault current dissipation in power plant grounding grids based on joint modeling. This method can accurately calculate the fault current dissipation in power plant grounding grids under different fault scenarios, thereby providing effective safety guidance for the construction and maintenance of grounding grids.

[0007] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions: The first aspect of this invention provides a method for calculating fault current dissipation in power plant grounding grids based on joint modeling.

[0008] A method for calculating fault current dissipation in power plant grounding grids based on joint modeling includes: Based on soil stratification parameters and grounding grid conductor network parameters, a joint model of stratified soil and conductor network is constructed. The soil stratification parameters are obtained through soil parameter inversion method. The grounding grid conductor network parameters are modeled by discretization to characterize the conductor's impedance and the node connection relationship between conductors. A hybrid numerical algorithm is used to calculate the joint model to determine the fault current distribution of the grounding grid. Specifically, the soil model characteristics and fault scenario types are judged. When the soil model is layered soil or the fault scenario is transient, the frequency domain method of moments is used to solve the fault current; otherwise, the time domain finite element method is used to solve the fault current. Based on the distribution of the fault current, the electrical safety parameters of the grounding grid are calculated; and the topology and materials of the grounding grid are adjusted according to the obtained electrical safety parameters.

[0009] Furthermore, the soil parameter inversion method includes: using the Winner quadrupole method to invert the soil data to be analyzed, and obtaining the resistivity and thickness of the layered soil as soil stratification parameters.

[0010] Furthermore, the discretization process includes: dividing the grounding grid conductor into multiple micro-segments, and defining intermediate nodes and end nodes for each micro-segment, so as to calculate the node potential and leakage current through a field-circuit combination method.

[0011] Furthermore, the frequency domain method of moments discretizes the surface of the grounding grid conductor only through boundary integral equations to reduce the computational degrees of freedom.

[0012] Furthermore, the time-domain finite element method solves Maxwell's equations by volume discretization and employs local mesh refinement technology in the high-gradient region for encryption processing; wherein, the high-gradient region includes the grounding grid edge region and the vertical grounding electrode connection region.

[0013] Furthermore, the topology of the grounding grid is adjusted, including adding at least one of a vertical grounding electrode and an equalizing ring, to adjust the current dissipation path of the fault current.

[0014] Furthermore, the materials of the grounding grid are adjusted, including filling high resistivity areas with resistance-reducing materials to correct the current dissipation path of fault current and reduce local impedance.

[0015] The second aspect of the present invention provides a power plant grounding grid fault current dissipation calculation system based on joint modeling.

[0016] A power plant grounding grid fault current dissipation calculation system based on joint modeling includes: The joint model construction module is configured to: construct a joint model of layered soil and conductor network based on soil stratification parameters and grounding grid conductor network parameters; wherein, the soil stratification parameters are obtained through soil parameter inversion method; the grounding grid conductor network parameters are modeled by discretization processing to characterize the conductor's own impedance and the node connection relationship between conductors; The hybrid numerical calculation module is configured to: use a hybrid numerical algorithm to calculate the joint model to determine the fault current distribution of the grounding grid, that is: judge the soil model characteristics and fault scenario type; when the soil model is layered soil or the fault scenario is a transient fault scenario, the frequency domain method of moments is used to solve the fault current; otherwise, the time domain finite element method is used to solve the fault current. The grounding grid fault current dissipation adjustment module is configured to: calculate the electrical safety parameters of the grounding grid based on the distribution of the fault current dissipation; and adjust the topology and materials of the grounding grid according to the obtained electrical safety parameters. A third aspect of the present invention provides a computer-readable storage medium having a program stored thereon, which, when executed by a processor, implements the steps in the power plant grounding grid fault current dissipation calculation method based on joint modeling as described in the first aspect of the present invention.

[0017] The fourth aspect of the present invention provides an electronic device, including a memory, a processor, and a program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps in the power plant grounding grid fault current dissipation calculation method based on joint modeling as described in the first aspect of the present invention.

[0018] The above one or more technical solutions have the following beneficial effects: This invention constructs a joint model of layered soil and conductor networks based on soil stratification parameters and grounding grid conductor network parameters. The soil stratification parameters are obtained through soil parameter inversion methods, while the grounding grid conductor network parameters are modeled through discretization. By discretizing the grounding grid conductor into multiple micro-segments and performing refined modeling combining field and circuit parameters, the resistance, inductance, and complex node connections of the conductors are accurately characterized, abandoning the unreasonable assumptions of existing methods that treat the grounding grid as an equipotential body or a homogeneous conductor. This modeling approach can realistically reflect the axial flow and leakage patterns of fault current in the grounding grid, thereby accurately calculating the hotspot areas and potential distribution of current dissipation. Based on this, the final evaluation results of key safety parameters such as step voltage and contact voltage are more reliable, providing a more accurate data foundation for the safety design of the grounding grid.

[0019] This invention constructs a three-dimensional non-uniformly layered soil model through the Wenner four-pole method and employs a hybrid numerical algorithm to simulate the non-uniform effects of soil stratification with different resistivity on the diffusion path, such as guidance and blockage. This method can accurately calculate the potential distribution in situations such as the presence of high-resistivity surface layers, effectively avoiding underestimation or overestimation of dangerous potentials due to model distortion. This allows the invention to dynamically adapt to various complex actual engineering geological conditions, significantly improving the accuracy of grounding safety assessments and the level of personal and equipment safety protection for power plants under different fault scenarios such as lightning strikes and short circuits.

[0020] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0022] Figure 1 This is a flowchart of the power plant grounding grid fault current dissipation calculation method based on joint modeling in Embodiment 1 of the present invention.

[0023] Figure 2 This is a schematic diagram of the discretization of the grounding grid conductor network in Embodiment 1 of the present invention.

[0024] Figure 3 This is a partial enlarged view of the discretized schematic diagram of the grounding grid conductor network in Embodiment 1 of the present invention.

[0025] Figure 4 This is a schematic diagram of the potential distribution in the fault current dissipation in Embodiment 1 of the present invention. Detailed Implementation

[0026] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0027] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations of the present invention.

[0028] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0029] Example 1 This embodiment discloses a method for calculating fault current dissipation in power plant grounding grids based on joint modeling.

[0030] like Figure 1 As shown, the method for calculating fault current dissipation in power plant grounding grids based on joint modeling includes: Step S1: Based on soil stratification parameters and grounding grid conductor network parameters, construct a joint model of stratified soil and conductor network; wherein, the soil stratification parameters are obtained through soil parameter inversion method; the grounding grid conductor network parameters are modeled by discretization processing to characterize the conductor's own impedance and the node connection relationship between conductors; Step S2: Use a hybrid numerical algorithm to calculate the joint model to determine the fault current distribution of the grounding grid. Specifically, judge the soil model characteristics and fault scenario type. When the soil model is layered soil or the fault scenario is a transient fault scenario, use the frequency domain method of moments to solve the fault current; otherwise, use the time domain finite element method to solve the fault current. Step S3: Based on the distribution of the fault current, calculate the electrical safety parameters of the grounding grid; and adjust the topology and materials of the grounding grid according to the obtained electrical safety parameters.

[0031] Based on the above process, this invention can accurately calculate the fault current dissipation of power plant grounding grids under different fault scenarios, thereby providing effective safety guidance for the construction and maintenance of grounding grids. To facilitate understanding of the technical solution of this invention, the specific implementation methods of this invention will be further explained and described below.

[0032] In step S1, a joint model of the layered soil and conductor network is constructed based on the soil stratification parameters and the grounding grid conductor network parameters.

[0033] Soil stratification parameters were obtained through a soil parameter inversion method, specifically: the Winner quadrupole method was used to invert the soil data under analysis to obtain the resistivity and thickness of the stratified soil layers as soil stratification parameters, in order to construct a three-dimensional non-uniform soil model. In the specific implementation process, firstly, on-site measurements were conducted using the Winner quadrupole method, obtaining apparent resistivity data at different depths by varying the electrode spacing; then, an optimized inversion algorithm was used to obtain the soil stratification structure parameters (number of layers, resistivity of each layer, and thickness); finally, a non-uniform model reflecting the three-dimensional distribution of soil resistivity in the station area was constructed through spatial interpolation, providing a realistic soil environmental background for subsequent accurate calculation of fault current dissipation.

[0034] The grounding grid conductor network parameters are modeled by discretization to characterize the conductor's impedance and the node connections between conductors. Specifically, the grounding grid conductor is divided into multiple micro-segments, and intermediate and terminal nodes are defined for each micro-segment to calculate node potentials and leakage currents using a field-circuit combined method. First, conductor segmentation (mesh partitioning) is performed: based on the grounding grid design drawings, the entire conductor is segmented using a linear micro-segment method, ensuring that the length of each micro-segment is much smaller than the wavelength corresponding to the highest frequency of the fault current. Then, node definition and network topology construction are performed: terminal nodes are defined at both ends of each conductor micro-segment to describe the network connection topology; intermediate nodes are defined at the center point of each micro-segment to characterize its impedance (resistance and inductance) and serve as the equivalent point for current leakage to the ground; based on electromagnetic field theory, the mutual resistance relationship (potential coefficient matrix) between all intermediate nodes of the micro-segments is established. Simultaneously, based on circuit theory, the discretized network is considered as a circuit with lumped parameter impedances (admittance matrix), and the system equations are solved simultaneously to obtain the potentials of all nodes and the leakage currents at each intermediate point.

[0035] like Figure 2 The diagram shown is a discretized schematic of the grounding grid conductor network. Figure 3 The enlarged view in the lower left corner of the network shown illustrates a modeling method that divides a continuous conductor into multiple micro-segments, setting end nodes (defining network connections) at the endpoints of each micro-segment and intermediate nodes (characterizing conductor impedance and leakage points) at the center. This discretized model accurately characterizes the topology and impedance of the conductor network, providing a foundation for subsequent field-circuit combined calculations of axial flow and radial leakage of fault current.

[0036] In step S2, a hybrid numerical algorithm is used to calculate the joint model to determine the fault current distribution of the grounding grid. Specifically, the soil model characteristics and fault scenario type are assessed. When the soil model is layered soil or the fault scenario is transient, the frequency domain method of moments is used to solve for the fault current; otherwise, the time domain finite element method is used. This can be achieved through the following methods: Step S2-1: Determine the characteristics of the soil model and the type of failure scenario.

[0037] The algorithm determines the soil model characteristics and fault scenario type by analyzing soil model parameters (number of layers, resistivity) and fault current characteristics (waveform spectrum). For layered soil or transient fault scenarios containing high-frequency components, the frequency domain method of moments is triggered; otherwise, the time domain finite element method is used. This judgment logic ensures that the hybrid numerical algorithm can adapt to different working conditions, balancing computational efficiency and accuracy.

[0038] Step S2-2: When the soil model is layered soil or the fault scenario is a transient fault scenario, the frequency domain moment method is used to solve the fault dispersion.

[0039] The Frequency Domain Method of Moments (MoM), based on boundary integral equations, requires only discrete conductor surfaces, significantly reducing computational degrees of freedom. It is particularly suitable for high-frequency transient scenarios such as lightning strikes and harmonics. Its frequency domain characteristics allow for direct analysis of complex frequency domain Green's functions, thus avoiding numerical oscillations caused by time-step limitations in time-domain algorithms. Furthermore, the "mathematical model for calculating the unequal potential of grounding system parameters" is the theoretical core and equation foundation of the MoM solution, transforming the physical problem into computable boundary integral equations. The "analysis and calculation of contact potential and step potential" represents a specific engineering application of the algorithm's results. The MoM, as a solver, connects the theoretical model with safety assessment applications.

[0040] 1) Mathematical model for calculating the unequal potential of grounding system parameters.

[0041] The potential at any point in the soil is generated by the source of leakage current in the soil. The grounding grid is a source of leakage current; the potential at any point near the substation is generated by it. By calculating the leakage current distribution on the grounding grid, the potential at the current injection point can be calculated, thus yielding the grounding resistance of the grounding grid. Simultaneously, the potentials of any two points on the ground surface can also be calculated, thus yielding the step voltage, contact voltage, and the potential difference between any grounding electrodes. Therefore, to accurately analyze the performance of the grounding grid in layered soil, the key is to obtain the distribution of leakage current in the conductors. In actual substations, the grounding grid is buried underground, making it difficult to obtain the leakage current of each part of the grounding electrode through measurement. Therefore, the electromagnetic field method is chosen to calculate the current distribution.

[0042] Assume there is a constant current Flow into the buried area with resistivity For electrodes in uniform soil, based on the steady-state current field theory and applying the principle of Green's function, with infinity as the reference point, the electrode discharge current at any point can be obtained. The generated potential is: ; in, Indicates electrode surface superior The leakage current density at the point; Green's formula, corresponding to the electrode geometry, is used to express the unit current flowing through the electrode surface. Dot at The potential generated at the point; Represents any point The potential value at that location.

[0043] The total discharge current flowing into the soil through the grounding grid is equal to the constant current injected into the grounding electrode. ,Right now: ; Applying the surface charge method to linear grounding electrodes involves appropriately dividing the linear electrode into... In another part, we will study the potential generated by the charge density of each part.

[0044] Since electric potential is a scalar and the earth is a linear medium, the potential at any point on the surface of the grounding electrode can be proven to be the sum of the potentials generated independently at that point by each line segment of the electrode. Therefore, complex grounding electrodes can be divided into many linear micro-segments for calculation.

[0045] Assuming the total length of the electrode is Through the total length of the electrodes The total current of the leakage is (i.e., a constant current injected into the ground electrode), will Divided into 1 micro-segment; of which, the first The length of a microsegment is represented as The center is represented as , No. The leakage current of the micro-segment is expressed as That's understandable. Therefore, we have: ; ; ; in, express The resistance value at the location.

[0046] Each Point fixed at the first electrode On the micro segment, then This represents the first Micro-segment and the first The mutual resistance between micro-segments, used subsequently Indicates. When hour, That is, the first Micro-segment self-resistance, i.e.: ( i =1, 2, ……, n ); in, express Voltage value at the location.

[0047] Since the grounding grid is not at equal potentials, a field-circuit combined calculation method is required. The basic idea of ​​field-circuit combined calculation is to add an intermediate node to each segment of the conductor, and to add the internal impedance of the metallic conductor between the intermediate node and the end node. The node equations are listed and solved using the nodal method in circuit theory, while the mutual resistance between conductor segments and the self-resistance of the conductor segments are still calculated using electromagnetic field theory. The internal impedance of the metal can be easily obtained from the conductor dimensions, its conductivity, and frequency. Assuming that the leakage current of each segmented conductor flows into the ground at the intermediate node, the midpoint potential matrix can be obtained by the following formula: ; in, Indicates an intermediate node. express Voltage value at the point; Represents the resistance matrix, when hour, For the first The self-resistance of a micro-segment, when unequal to the resistance of the two, represents the mutual resistance between the conductor segments. Therefore, the grounding system after the intermediate node can be considered equivalent to a circuit network. Based on this, this embodiment expresses this circuit network as nodal equations: ; in, Indicates the end nodes of the subdivision segment; This represents the column vector of injected current at the end nodes. Only short-circuit nodes have current injected into the grounding system, while the injected current at the other nodes is zero. This represents the self-guided diagonal matrix of intermediate nodes, whose elements can be calculated using the resistance formula for metallic conductors. This indicates the mutual conductivity between intermediate nodes and end nodes, when the node and nodes When connected, the element value is the self-admittance of the conductor segment between them, and the element value is negative; when the nodes are not connected, the element value is zero. express The transpose of the matrix, Represents the diagonal matrix of self-admittance of the end nodes; express Voltage value at point express Voltage value at the location; express The current value at the point.

[0048] Based on the above formula and combined with the following formula, the potentials at the midpoint and end points of the split conductor segment and the leakage current flowing into the ground at the midpoint can be obtained, that is: ; in, This is expressed as follows. After obtaining the ground current of each conductor segment from this formula, the potential of the grounding system at the current injection point can be calculated according to electric field theory. This potential divided by the current injected into the grounding grid is the grounding resistance of the grounding grid. Alternatively, the potential at each point of the grounding conductor can be calculated, and the axial current distribution on the grounding grid can be determined from these potentials.

[0049] 2) Analysis and calculation of contact potential and step potential.

[0050] According to the power industry grounding code DL / T621-1997, when a single-phase grounding or a two-phase grounding at the same point occurs in an effective grounding system of 110kV and above and a low-resistance grounding system of 6~35kV, the maximum limits for the contact voltage and step voltage of the substation grounding device are as follows: ; ; in, Indicates the resistivity of the surface layer. Indicates the duration of the short-circuit current; This indicates the maximum limit of the contact voltage of the substation grounding device. These represent the maximum limit for the step voltage of the substation grounding device. These two maximum limits are derived from a human body weighing 50 kg.

[0051] Based on this, a correction factor is introduced to consider the thickness of the high-resistivity layer on the surface and the influence of the soil beneath the high-resistivity layer on the resistance of human feet, namely: ; in, Indicates the thickness of the high resistivity protective layer on the Earth's surface; This represents the correction factor for the grounding resistance of the foot when a high-resistivity layer is present. This represents the reflection coefficient between the surface high-resistivity layer and the underlying soil layer, and ; Represents the empirically fitted parameters. This represents an empirical constant (usually 0.08 or 0.09).

[0052] Under the IEEE Std80 standard, the maximum permissible contact voltage for a human body weighing 50kg is... and step voltage They are respectively: ; ; Correction coefficient It can be approximated by the following formula: ; Where, constant Reflectance coefficient The value ranges from 0 to -0.98, and the thickness of the high resistivity protective layer on the earth's surface is... The value is 0~0.3 m. By comparing with the analytical solution, the error of the above formula is less than 5%.

[0053] The formulas for calculating contact voltage and step voltage using DL / T621 only consider the soil resistivity at the point where a person stands. Therefore, when a high-resistivity layer is used, the permissible contact voltage and step voltage will increase, but the formulas cannot reflect the effect of the high-resistivity layer thickness. In contrast, the corresponding formulas using IEEE Std80 consider both the resistivity and thickness of the surface soil layer and the resistivity of the subsurface soil. Furthermore, in the formulas for calculating contact voltage and step voltage, the human body resistance is taken as 1500Ω under the DL / T621 standard, while it is taken as 1000Ω under the IEEE Std80 standard.

[0054] Therefore, in this embodiment, considering both DL / T621 and IEEE Std80, the human body resistance is set at 1500 ohms. Simultaneously, a surface attenuation factor is introduced according to the IEEE standard, and the actual calculations of step voltage and contact voltage are performed using the following formula: ; ; ; in, Indicates step voltage. This indicates the contact voltage.

[0055] Step S2-3: When the soil model does not belong to layered soil and the fault scenario is not a transient fault scenario, the time-domain finite element method is used to solve the fault dispersion.

[0056] The finite-element time-domain (FEM) method directly solves Maxwell's equations through volume discretization, making it particularly suitable for non-uniform soils. Furthermore, meshing techniques can be used to locally refine high-gradient regions (such as the edges of grounding grids) to improve the accuracy of step voltage calculations.

[0057] The finite element method (FEM) is an effective method for calculating and analyzing the potential distribution of a grounding grid. Its basic idea is to decompose the solution domain of a complex continuous medium into a finite number of simple-shaped sub-regions, forming an equivalent discrete region of the original region. This simplifies the problem of solving the field variables of a continuous medium into solving the problem of solving the field variables at a finite number of element nodes, making it very suitable for handling complex boundary conditions in the presence of a grounding grid. For solving a practical physical problem, the FEM solution can be divided into the following five steps: 1) List the governing equations of the solution domain of the physical problem to be solved and determine the corresponding boundary conditions for each boundary; 2) Partition the field domain, reasonably determine the mesh size and growth rate parameters based on the geometric structure of the solution domain, and discretize the solution domain; 3) Determine the interpolation function of the discrete elements and derive the discrete finite element algebraic equations using variational methods; 4) Solve the equations using either a direct method or an iterative method. The direct method has good convergence but consumes the most computational resources; the iterative method is the opposite; 5) Post-processing of the solution results.

[0058] In grounding grid modeling and analysis, the most important aspect is to theoretically model the shape and structure of the grounding grid, soil resistivity, and soil structure. Typically, a physical model of the grounding conductor in a semi-infinite medium (soil) is established. Soil structure can be divided into multi-layered structures with horizontal and vertical layers, which can improve the accuracy of the calculation results.

[0059] The finite element method (FEM) was used to analyze and calculate the entire physical model. First, soil resistivity was tested to obtain an actual earth soil model. Based on the complexity of the actual situation, the soil model was multi-layered, resulting in a multi-layered soil model. According to the grounding grid model, spatial coordinate transformation can be used to transform the infinite open-ended current distribution region into a finite closed region through linear coordinate transformation. Within the finite closed region, the grounding resistance of the grounding grid was calculated using the FEM method. The step voltage and contact voltage generated when the fault current enters the ground were calculated and compared with relevant national standards and IEEE standards. The grounding grid structural parameters were optimized and adjusted to obtain an optimized grounding grid model. The calculation was repeated iteratively until the grounding grid model met the design requirements. Finally, a 3D model was drawn using the 3D mesh data and potential calculation results, combined with computer graphics.

[0060] The current density vector in a conductor exhibits a non-uniform distribution due to the conductor's geometry. By establishing equations related to the current field and solving them using the finite element method, the current density vector distribution in the target region of the conductor can be obtained, allowing for the calculation of ohmic losses, etc. Under steady-state conditions, the current density vector can be expressed using Ohm's theorem as: ; in, For current density, For electric field, is the electrical conductivity.

[0061] The electric field can be expressed as the gradient of potential energy, that is: ; in, For electric field, It represents the electric potential.

[0062] According to the continuity equation Finally, we can obtain the equation satisfied by the scalar potential in the steady-state current field: ; in, For electrical conductivity, denoted as current density.

[0063] Its expression is similar to the equation for a static electric field, except that the coefficients are replaced by conductivity instead of dielectric constant. Furthermore, the current density vector along the cross-section flowing through the conductor must satisfy constraint equations: ; in, For current density, For area, For electrical conductivity, For electric potential, It represents electric current.

[0064] By combining the above equations, the potential energy distribution in the steady-state current field can be calculated, and then physical quantities such as the current density vector in space can be calculated.

[0065] Step S2 yields the distribution of fault current dissipation. Specifically, numerical calculations using the frequency domain method of moments (S2-2) and the time domain finite element method (S2-3) are performed to obtain the axial current values ​​of all discrete micro-segments on the entire grounding grid conductor, as well as the leakage current density flowing from each intermediate node into the surrounding soil. These data collectively constitute the distribution of fault current dissipation: the axial current distribution reveals the flow path and hotspots of the fault current within the conductor network; the leakage current density visually reflects the spatial distribution of current leaking from the conductor surface into the soil, identifying areas of strong and weak current dissipation.

[0066] like Figure 4 The diagram shows the potential distribution of fault current dissipation. The vertical axis represents voltage values, used to illustrate potential changes in different areas. The color and numerical gradient reflect the attenuation of potential from the grounding grid to distant locations. High-value areas are current concentration points, while low-value areas are current diffusion areas, which can identify dangerous potential zones.

[0067] In step S3, the electrical safety parameters of the grounding grid are calculated based on the distribution of fault current; and the topology and materials of the grounding grid are adjusted according to the obtained electrical safety parameters.

[0068] Based on the distribution of fault current, the electrical safety parameters of the grounding grid are calculated. Specifically, based on the potential of each point obtained from the current distribution, the contact voltage (the potential difference between a human body contacting equipment and the ground) is calculated according to DL / T621 and IEEE Std80 standards.

[0069] Based on the obtained electrical safety parameters, the topology of the grounding grid is adjusted by adding at least one of vertical grounding electrodes and equalizing rings to adjust the current dissipation path of fault current. Specifically, if the step voltage exceeds the standard, vertical grounding electrodes are added in the current-dense area to enhance current discharge; if the contact voltage is uneven, equalizing rings are added around the equipment to make the potential distribution more uniform and optimize the current dissipation path.

[0070] Based on the obtained electrical safety parameters, the materials of the grounding grid are adjusted by filling high resistivity areas with resistance-reducing materials to correct the current dissipation path of the fault and reduce local impedance. Specifically, the high-resistivity area is first located and filled with a resistance-reducing agent (such as bentonite) to reduce the local soil resistivity, making the current dissipation smoother, reducing impedance, and avoiding excessively high local potential to ensure safety.

[0071] Example 2 This embodiment discloses a power plant grounding grid fault current dissipation calculation system based on joint modeling.

[0072] A power plant grounding grid fault current dissipation calculation system based on joint modeling includes: The joint model construction module is configured to: construct a joint model of layered soil and conductor network based on soil stratification parameters and grounding grid conductor network parameters; wherein, the soil stratification parameters are obtained through soil parameter inversion method; the grounding grid conductor network parameters are modeled by discretization processing to characterize the conductor's own impedance and the node connection relationship between conductors; The hybrid numerical calculation module is configured to: use a hybrid numerical algorithm to calculate the joint model to determine the fault current distribution of the grounding grid, that is: judge the soil model characteristics and fault scenario type; when the soil model is layered soil or the fault scenario is a transient fault scenario, the frequency domain method of moments is used to solve the fault current; otherwise, the time domain finite element method is used to solve the fault current. The grounding grid fault current dissipation adjustment module is configured to: calculate the electrical safety parameters of the grounding grid based on the distribution of the fault current dissipation; and adjust the topology and materials of the grounding grid according to the obtained electrical safety parameters. Example 3 The purpose of this embodiment is to provide a computer-readable storage medium.

[0073] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps in the power plant grounding grid fault current dissipation calculation method based on joint modeling as described in Embodiment 1 of this disclosure.

[0074] Example 4 The purpose of this embodiment is to provide an electronic device.

[0075] An electronic device includes a memory, a processor, and a program stored in the memory and executable on the processor. When the processor executes the program, it implements the steps in the power plant grounding grid fault current dissipation calculation method based on joint modeling as described in Embodiment 1 of this disclosure.

[0076] The steps and methods involved in the apparatuses of Embodiments 2, 3, and 4 above correspond to those in Embodiment 1. For specific implementation details, please refer to the relevant description section of Embodiment 1. The term "computer-readable storage medium" should be understood as a single medium or multiple media including one or more instruction sets; it should also be understood as including any medium capable of storing, encoding, or carrying an instruction set for execution by a processor and enabling the processor to perform any of the methods in this invention.

[0077] Those skilled in the art will understand that the modules or steps of the present invention described above can be implemented using general-purpose computer devices. Optionally, they can be implemented using computer-executable program code, thereby allowing them to be stored in a storage device for execution by a computer device, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. The present invention is not limited to any particular combination of hardware and software.

[0078] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for calculating fault current dissipation in power plant grounding grids based on joint modeling, characterized in that, include: Based on soil stratification parameters and grounding grid conductor network parameters, a joint model of stratified soil and conductor network is constructed. The soil stratification parameters are obtained through soil parameter inversion method. The grounding grid conductor network parameters are modeled by discretization to characterize the conductor's impedance and the node connection relationship between conductors. A hybrid numerical algorithm is used to calculate the joint model to determine the fault current distribution of the grounding grid. Specifically, the soil model characteristics and fault scenario types are judged. When the soil model is layered soil or the fault scenario is transient, the frequency domain method of moments is used to solve the fault current; otherwise, the time domain finite element method is used to solve the fault current. Based on the distribution of the fault current, the electrical safety parameters of the grounding grid are calculated; and the topology and materials of the grounding grid are adjusted according to the obtained electrical safety parameters.

2. The method for calculating fault current dissipation in power plant grounding grids based on joint modeling as described in claim 1, characterized in that, The soil parameter inversion method includes: using the Winner quadrupole method to invert the soil data to be analyzed, and obtaining the resistivity and thickness of the layered soil as soil stratification parameters.

3. The method for calculating fault current dissipation in power plant grounding grids based on joint modeling as described in claim 1, characterized in that, The discretization process includes: dividing the grounding grid conductor into multiple micro-segments, and defining intermediate nodes and end nodes for each micro-segment, so as to calculate the node potential and leakage current through the field-circuit combination method.

4. The method for calculating fault current dissipation in power plant grounding grids based on joint modeling as described in claim 1, characterized in that, The frequency domain method of moments reduces the computational degrees of freedom by discretizing the surface of the grounding grid conductor only through boundary integral equations.

5. The method for calculating fault current dissipation in power plant grounding grids based on joint modeling as described in claim 1, characterized in that, The time-domain finite element method solves Maxwell's equations by volume discretization and uses a local mesh refinement technique in the high-gradient region for encryption processing; wherein, the high-gradient region includes the grounding grid edge region and the vertical grounding electrode connection region.

6. The method for calculating fault current dissipation in power plant grounding grids based on joint modeling as described in claim 1, characterized in that, Adjusting the topology of the grounding grid includes adding at least one of vertical grounding electrodes and equalizing rings to adjust the current dissipation path of fault current.

7. The method for calculating fault current dissipation in power plant grounding grids based on joint modeling as described in claim 1, characterized in that, Adjustments are made to the materials of the grounding grid, including filling high resistivity areas with resistance-reducing materials to correct the current dissipation path of fault currents and reduce local impedance.

8. A power plant grounding grid fault current dissipation calculation system based on joint modeling, characterized in that, include: The joint model construction module is configured to: construct a joint model of layered soil and conductor network based on soil stratification parameters and grounding grid conductor network parameters; wherein, the soil stratification parameters are obtained through soil parameter inversion method; the grounding grid conductor network parameters are modeled by discretization processing to characterize the conductor's own impedance and the node connection relationship between conductors; The hybrid numerical calculation module is configured to: use a hybrid numerical algorithm to calculate the joint model to determine the fault current distribution of the grounding grid, that is: judge the soil model characteristics and fault scenario type; when the soil model is layered soil or the fault scenario is a transient fault scenario, the frequency domain method of moments is used to solve the fault current; otherwise, the time domain finite element method is used to solve the fault current. The grounding grid fault current dissipation adjustment module is configured to: calculate the electrical safety parameters of the grounding grid based on the distribution of the fault current dissipation; and adjust the topology and materials of the grounding grid according to the obtained electrical safety parameters.

9. A computer-readable storage medium having a program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps in the power plant grounding grid fault current dissipation calculation method based on joint modeling as described in any one of claims 1-7.

10. An electronic device, comprising a memory, a processor, and a program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps in the power plant grounding grid fault current dissipation calculation method based on joint modeling as described in any one of claims 1-7.

Images