High resistance ground fault resistance modeling and detection method and system considering medium ion migration

Abstract

This invention discloses a method and system for modeling and detecting grounding resistance in high-resistivity faults, considering dielectric ion migration, belonging to the field of power system fault detection technology. The method includes: establishing an integral model of grounding resistance based on the physical mechanism of ion electromigration in the dielectric and hemispherical theory. This integral model is a nonlinear integral expression of dielectric ion concentration and current dispersion radius; establishing an explicit mathematical relationship between dielectric ion conductivity and fault current and dispersion radius through three-dimensional fitting of a surface; and finally substituting this explicit mathematical relationship into the nonlinear integral expression of grounding resistance to solve for the analytical model of dynamic grounding resistance with respect to fault current. This invention accurately characterizes the nonlinear time-varying characteristics of grounding resistance under high-resistivity faults, providing a theoretical basis for reliable detection of high-resistivity faults. Simulation and real-world experimental results show that this method maintains high fidelity under different grounding media, with waveform similarity exceeding 0.997.

Description

Technical Field

[0001] This invention belongs to the field of power system fault detection technology, specifically relating to a method and system for modeling and detecting high-resistance fault grounding resistance considering dielectric ion migration for high-resistance grounding fault analysis in distribution networks. Background Technology

[0002] Accurate analysis of HIF (High-Impedance Fault) in distribution networks relies on precise modeling of grounding resistance characteristics. As a critical component of the fault loop, the dynamic nonlinear characteristics of grounding resistance directly affect the amplitude and waveform of the fault current, thus determining the reliability of HIF detection and protection. Traditional grounding resistance calculation methods have significant limitations and struggle to accurately characterize the dynamic processes under HIF conditions.

[0003] Early studies typically simplified grounding resistance to a linear model, neglecting soil ionization and nonlinear effects. For example, EE Oettle proposed a formula for calculating grounding resistance R based on the assumption of uniform soil in "A new general estimation curve for predicting the impulse impedance of centralized grounding electrodes" (IEEE Transactions on Power Delivery, 2005, 3(4): 2020-2029): R = ρ / 2πr, where ρ is the soil resistivity and r is the soil dispersion radius. This method treats ρ as a constant, completely ignoring the nonlinear change in soil resistivity with electric field strength after fault current injection.

[0004] To improve accuracy, Wang Bin et al., in their paper "Analysis and Detection of Volt-Ampere Characteristics of High-Resistance Grounding Faults in Distribution Networks" (Proceedings of the CSEE, 2014, 34(22): 3815-3823), equated the HIF path to a series connection of a linear resistance and an arc resistance, but did not consider the dynamic resistance changes caused by the ionization process of the grounding medium itself. Although this method partially reflects the arc characteristics, it cannot describe the impedance nonlinearity caused by soil ion migration.

[0005] Under high electric fields, soil ionization occurs in grounding resistance, leading to a significant decrease in resistivity. Chen Xianlu et al. analyzed the impact characteristics of grounding bodies in detail in their classic work "Grounding" (Chongqing University Press, 2002), but did not provide a dynamic resistance model based on ion migration. This model is applicable to steady-state or low-frequency conditions and cannot capture the resistance changes during the HIF transient process.

[0006] To avoid the complexity of physical modeling, numerical methods are widely used. In their paper "Finite Element Model of Grounding Body Considering Soil Ionization Dynamic Process" (Proceedings of the CSEE, 2011, 31(22): 149-157), Sima Wenxia et al. used the finite element method to simulate soil ionization and fitted the grounding resistance with empirical formulas. However, the model relied on a large number of simulation parameters and lacked universality.

[0007] Some studies model grounding impedance from the frequency domain perspective. MAO Schroeder et al. calculated grounding resistance through frequency domain analysis in "Transient grounding behavior considering frequency-dependent soil parameters: a comparison of field theory and transmission line theory" (2017 IEEE 3rd Global Electromagnetic Compatibility Conference (GEMCCON), Sao Paulo, Brazil, 2017:1-5). However, the model could not reflect the time-varying characteristics of resistance under power frequency faults and ignored the physical nature of ion migration.

[0008] In summary, existing methods for calculating HIF grounding resistance have four main shortcomings:

[0009] 1. Traditional models do not start from the microscopic physical processes of ion migration and cannot explain the dynamic change mechanism of grounding resistance under fault current.

[0010] 2. Soil resistivity is treated as a constant or a simple linear parameter, ignoring its nonlinear decay characteristics with electric field strength.

[0011] 3. Most models lack real-world experimental data to support them, making it difficult to guarantee their practicality in engineering.

[0012] 4. The model parameters are fixed and cannot adapt to the changes in the characteristics of different grounding media (such as red soil and fine sand). Summary of the Invention

[0013] This invention aims to address the technical problems of existing grounding resistance models not fully considering the physical mechanisms of ion migration and the need to improve model accuracy. To this end, the technical solution of this invention provides a method and system for modeling and detecting high-resistance fault grounding resistance that considers ion migration in the medium. This method, starting from the physical mechanism of ion electromigration, proposes a grounding resistance integral model constructed based on the physical mechanism of ion electromigration in the soil medium. This gives the model a clear physical meaning, overcoming the black-box problem of traditional data-driven methods. Furthermore, this grounding resistance integral model or analytical grounding resistance model is applicable to different soil media; by adjusting the parameters, it can meet the requirements of the corresponding soil medium, making it more versatile than existing technologies.

[0014] Therefore, the present invention provides the following technical solution:

[0015] On one hand, the present invention provides a method for modeling high-resistivity fault grounding resistance considering dielectric ion migration, comprising the following steps:

[0016] An integral model of grounding resistance is established based on the physical mechanism of ion electromigration in soil media. This model represents the grounding resistance of a high-resistance fault with respect to the ion conductivity ∑|z. i |C i The nonlinear integral expressions for μ and the divergence radius r, z i C represents the valence charge of the i-th type ion. i Let μ be the concentration of type i ions in the soil medium. i Let be the electromobility of the i-th type of ion;

[0017] Experiments were conducted on the target soil medium, and the ionic conductivity ∑|z was fitted based on the experimental data. i |C i μ i The explicit relationship between fault current I and dissipation radius r;

[0018] Substituting the explicit relational expression into the grounding resistance integral model yields the analytical model of grounding resistance for the target soil medium, which is an analytical expression of grounding resistance with respect to fault current I.

[0019] Optionally, the mathematical expression of the grounding resistance integral model is as follows:

[0020]

[0021] In the formula, R c For grounding resistance, The radius of the electric arc is denoted as .

[0022] Optionally, the process of constructing the grounding resistance integral model includes:

[0023] First, based on the theory of ion electromigration, a physical model of soil resistivity is established:

[0024] Soil resistivity ρ is the sum of electric field strength and the total current density of ions in the soil medium (J). c The ratio of to is used to characterize the soil medium's ability to impede electric current; the total current density of ions J c It is obtained by summing the products of the electromigration flux and the valence charge number of each ion, satisfying: , where J i Let E be the electromigration flux of the i-th type ion, and E be the electric field strength.

[0025] Secondly, based on the grounding resistance R under a high-resistance grounding fault (HIF) cThe physical model uses soil resistivity ρ to characterize grounding resistance R. c Nonlinearity;

[0026] Among them, the grounding resistance R c The physical model refers to a hemispherical conductive shell radiating from the arc point source to infinity. Based on this hemispherical conductive shell, the grounding resistance R is further... c The total resistance is obtained by integrating a series of differential hemispherical shell resistances of thickness dr. The resulting integral model of the grounding resistance is expressed as: .

[0027] Optionally, the ionic conductivity ∑|z i |C i μ i The explicit relationship between the fault current I and the divergence radius r is based on the ionic conductivity ∑|z i |C i μ i The optimal relationship expression is derived by fitting experimental data and is related to the fault current I and the current dissipation radius r.

[0028] The ionic conductivity ∑|z i |C i μ i The correlation between the fault current I and the current dissipation radius r is obtained as follows:

[0029] Repeated current impact tests were conducted on the target soil medium to obtain the curve of soil resistivity ρ as a function of electric field strength E, and then the relationship between soil resistivity ρ and electric field strength E was fitted.

[0030] Based on the relationship between electric field strength E and divergence radius r: E=Iρ / (2πr) 2 The relationship between soil resistivity ρ and electric field strength E, along with a physical model of soil resistivity based on ion electromigration theory, leads to a mathematical model of the correlation.

[0031] The physical model for the soil resistivity is expressed mathematically as follows: J c The total current density of the soil medium.

[0032] Optionally, the ionic conductivity ∑|z is used to fit the ionic conductivity. i |C i μ i The experimental data showing the relationship between the fault current I and the spill radius r were obtained by taking multiple values ​​of the spill radius r and the fault current I during the current impulse test.

[0033] Optionally, the analytical model of the grounding resistance is:

[0034]

[0035] In the formula, R c p1 represents the grounding resistance, and p2, p3, p4, and p5 are fitting parameters for the soil medium.

[0036] Optionally, the fitted ionic conductivity ∑|z i |C i μ i The relationship between the fault current I and the current dissipation radius r is as follows:

[0037] ;

[0038] In the formula, e is the natural base.

[0039] Secondly, the present invention provides a method for detecting high-resistivity fault grounding resistance considering dielectric ion migration, comprising:

[0040] An analytical model of grounding resistance is constructed using the method described above;

[0041] The grounding resistance detection results are obtained based on the analytical model of grounding resistance and the fault current at the time of detection.

[0042] In three aspects, the present invention provides a computer terminal, comprising: one or more processors; and a memory storing one or more computer programs; wherein the processor invokes the computer programs to implement:

[0043] The steps of the above-mentioned high-resistivity fault grounding resistance modeling method considering dielectric ion migration or the steps of the above-mentioned high-resistivity fault grounding resistance detection method considering dielectric ion migration.

[0044] In three aspects, the present invention provides a power distribution network system for conducting real-world tests on target soil media, the power distribution network system comprising:

[0045] Low-voltage power supply: used to provide power;

[0046] Step-up transformer: The low-voltage side of the step-up transformer is connected to the low-voltage power supply to boost the voltage of the low-voltage power supply to the high voltage level required for the full-scale test;

[0047] Busbar: Connected to the high-voltage side of the step-up transformer and serving as the power distribution hub, receiving high-voltage electricity from the step-up transformer and distributing it to the test circuit;

[0048] Grounding conductor: As the high-voltage electrode of the test circuit, one end is connected to the busbar and the other end is laid on the target soil medium to form a current channel to simulate a high-resistance grounding fault.

[0049] Signal detection equipment: including current transformers and voltage transformers, used to accurately measure the fault current flowing into the target soil medium and the fault voltage applied to the target soil medium;

[0050] Insulators: live parts of busbars and grounding conductors that are fixed and supported in the test site to ensure safe electrical isolation from the ground and surrounding objects;

[0051] Among them, the test data based on the full-scale test of the power distribution network system is used to fit the explicit relationship in the above method.

[0052] Compared with the prior art, the present invention achieves the following progress and effects:

[0053] This invention proposes a grounding resistance integral model based on the physical mechanism of ion electromigration in soil media, starting from the microscopic process of ion migration. This model has clear physical meaning and overcomes the black-box problem of traditional data-driven methods. Through fitting with real-world experimental data, the waveform similarity exceeds 0.997 under different grounding media, accurately reproducing key features such as "zero rest". The final model yields an analytical grounding resistance model with high computational efficiency, which can be embedded in protection device algorithms. The method can be adapted to different media types, such as red soil and fine sand, through parameter adjustment.

[0054] Compared with existing technologies, this invention overcomes the limitations of traditional methods that treat grounding resistance as a linear or constant parameter, accurately characterizes the nonlinear time-varying characteristics of grounding resistance under high-resistance faults, and provides a theoretical basis for reliable detection of high-resistance faults. Attached Figure Description

[0055] Figure 1 This is a flowchart of the method described in the embodiments of this application.

[0056] Figure 2 This is the wiring diagram for a real-world test field of a power distribution network.

[0057] Figure 3 This is a schematic diagram of the physical development mechanism of HIF.

[0058] Figure 4 It is a curve showing the relationship between soil resistivity and electric field strength.

[0059] Figure 5 It is a surface showing the variation of soil ionic conductivity with arc current and divergence radius.

[0060] Figures 6a-6d These are the waveforms of fault current, voltage, arc resistance, and grounding resistance under red soil. Figure 6a The fault current waveform is shown. Figure 6b This is the fault voltage waveform. Figure 6c This is the waveform of the arc resistance. Figure 6dThis is the waveform of the grounding resistance.

[0061] Figure 7 This is the fault resistance waveform under red soil.

[0062] Figures 8a-8d It is a comparison of the resistance waveforms of the actual test and the model. Figure 8a Corresponding to red soil, Figure 8b Corresponding to fine sand, Figure 8c Corresponding to loess soil, Figure 8d Corresponding to sandy soil. Detailed Implementation

[0063] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. The technical features involved in the various embodiments of the invention described below can be combined with each other as long as they do not conflict with each other.

[0064] It should be noted that although functional modules are divided in the device schematic diagram and a logical order is shown in the flowchart, in some cases, the steps shown or described may be performed in a different order than the module division in the device or the order in the flowchart. The terms "first," "second," etc., in the specification, claims, and the aforementioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0065] Unless otherwise defined, 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 application belongs. The terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit this application.

[0066] This invention provides a method and system for modeling and detecting high-resistivity fault grounding resistance considering ion migration in the medium. An integral model of grounding resistance is established based on the physical mechanism of ion electromigration in the soil medium. This integral model represents the high-resistivity fault grounding resistance with respect to the ion conductivity ∑|z i |C iThe nonlinear integral expressions for μ and the current diffusion radius r are essentially also nonlinear integral expressions for the high-resistivity fault grounding resistance with respect to the dielectric ion concentration and the current diffusion radius. Since the proposed grounding resistance integral model is derived from the physical mechanism of ion electromigration, it essentially solves the problem of decreased model accuracy caused by the traditional grounding resistance model's failure to fully consider the physical mechanism of ion migration. Furthermore, the analytical grounding resistance model constructed based on the grounding resistance integral model of this invention is applicable to different soil media. By adjusting the parameters, it can meet the needs of various soil media, making it more universal and applicable for wider application. Specifically, the model parameters for different media are preferably obtained through real-world experiments. Specifically, by conducting repeated current impact tests on various types of grounding media (such as soil) under specific ambient temperatures and soil moisture content, the resistivity variation curve with electric field strength can be obtained, thereby fitting its nonlinear decay model. Furthermore, through three-dimensional fitting surfaces, an explicit mathematical relationship between the dielectric ion conductivity and the fault current and diffusion radius can be established, which is used to update the model parameters corresponding to different soil media.

[0067] The embodiments of the present invention will be described in detail below. These embodiments are based on the technical solutions of the present invention and provide detailed implementation methods and specific operation processes.

[0068] This embodiment provides a method for modeling the grounding resistance of high-resistivity faults considering dielectric ion migration. Taking a high-resistivity grounding fault in red soil of a 10kV distribution network as an example, refer to... Figure 2 As shown, a realistic simulation of a high-resistance ground fault (HIF) is conducted in a test field for a new type of distribution network with an ungrounded neutral point. The corresponding distribution network system includes:

[0069] Low-voltage power supply: Used to provide power and is the energy starting point of the entire test system. In this embodiment, a controllable and stable 400V power supply with power frequency or a specific waveform is provided.

[0070] Step-up transformer: The low-voltage side of the step-up transformer is connected to the low-voltage power supply, boosting the voltage of the low-voltage power supply to the high voltage level required for the full-scale test. In this embodiment, the voltage is boosted to 10kV using a step-up transformer.

[0071] Busbar: Connected to the high-voltage side of the step-up transformer and serving as the power distribution hub, receiving high-voltage electricity from the step-up transformer and distributing it to the test circuit.

[0072] Grounding conductor: Serving as the high-voltage electrode in the test circuit, one end is connected to the busbar (high-voltage end), and the other end is laid on the target soil medium to form a current path, used to simulate a high-resistance grounding fault. For example... Figure 2 As shown, a grounding conductor is led out from line L1 3km away from the busbar, and the grounding conductor is placed flat on top of different soil media (such as red soil media) to form sufficient contact.

[0073] Signal detection equipment: including current transformers and voltage transformers, used to accurately measure the fault current flowing into the target soil medium and the fault voltage applied to the target soil medium. For example... Figure 2 The signal detection equipment in the system monitors the voltage and current waveforms of each line in real time using a waveform recording device with a sampling rate of 10kHz. Data sequences are extracted using a fixed-time window with a width of 100 data points, and a total of 32 sets of data segments from HIF tests of different media types are collected, namely the voltage and current data generated by the fault.

[0074] Insulators: The live parts of busbars and grounding conductors that are fixed and supported in the test site to ensure safe electrical isolation from the ground and surrounding objects.

[0075] The connection relationship of the above components can be briefly described as follows: Low-voltage power supply output terminal → connected to the low-voltage side of the step-up transformer → high-voltage side of the step-up transformer → connected to the busbar → grounding wire (as high-voltage electrode) led out from the busbar → laid in the target soil medium → after the current is dispersed through the soil, it returns to the neutral point of the step-up transformer via the earth or forms a loop. Brief description of the test procedure:

[0076] Deployment: On a selected typical soil site, the grounding conductor is buried at a predetermined depth and in a predetermined shape (such as a straight line or a ring) to construct the grounding electrode.

[0077] Wiring: Build the system according to the above connection relationship, check the range of the signal detection equipment, and set up the safety fence.

[0078] Pressure test: Start the low-voltage power supply and gradually increase the voltage through the step-up transformer. The grounding wire introduces the high voltage into the soil to simulate a high-resistance grounding fault point.

[0079] Data Acquisition: At each stable voltage level, the loop current and grounding electrode voltage to ground are simultaneously acquired using signal detection equipment. For different soil media, the soil type can be changed, and a waveform data segment can be divided into multiple segments of 100 data points each. Steps 3-4 are repeated to acquire multiple sets of data.

[0080] like Figure 1 The framework shown in this embodiment provides a method for modeling high-resistivity fault grounding resistance considering dielectric ion migration, including the following steps:

[0081] Step 1: Establish an integral model for grounding resistance based on the physical mechanism of ion electromigration in the soil medium. The specific process is as follows:

[0082] Step 11: Based on the theory of ion electromigration, establish a physical model of soil resistivity. The electrical conductivity pathways in the soil medium mainly include two parts: electronic conduction through the solid framework and ion migration through the fluid within the pores. For cases where multiple ions participate in electrical conductivity in the soil medium, the electromigration flux J of the i-th type of ion... i Calculated by equation (1):

[0083] (1)

[0084] In the formula, z i C is the valence charge number of the i-th type ion; i The concentration of type i ions in the soil medium; E is the electric field strength; μ i Let be the electromobility of the i-th type of ion.

[0085] Total current density of ions in soil medium J c It is obtained by summing the products of the electromigration flux and the valence charge number of each ion:

[0086] (2)

[0087] In the formula, |z i |C i Let ∑|z represent the total charge carried by the i-th freely moving ion within a unit cube; i |C i μ i This represents the conductivity of the i-th type of ions in the medium.

[0088] Soil resistivity ρ is essentially the ability of the soil medium to impede electric current, and its mathematical expression is:

[0089] (3)

[0090] Step 12, based on the grounding resistance R under high-resistance grounding fault (HIF) c The physical model uses soil resistivity ρ to characterize grounding resistance R. c Nonlinearity.

[0091] When a high-resistance ground fault (HIF) occurs, regardless of whether the grounding conductor is in contact with the soil medium, an arc resistance R will be formed as long as the power supply voltage is greater than the air gap breakdown voltage. arc After the fault arc is generated, the arc channel connects the grounding conductor and the soil medium together, with the contact surface having a radius of r. a The circle (for an electric arc burning in air, the radius r of the arc is generally considered to be...) a It is proportional to the square root of the arc current I, that is... The fault current flows into the ground through the contact surface, and the soil resistance through which it flows is the grounding resistance R.c The soil resistivity ρ changes dynamically and nonlinearly with the migration and differentiation of ions under the influence of fault current.

[0092] Based on the above analysis, taking overhead lines as an example, the HIF current channel structure is as follows: Figure 3 As shown. Compared to existing HIF models, the model constructed in this invention... Figure 3 The model shown focuses on the physical process of nonlinear change in grounding resistance and has a clear physical meaning. Among them, the arc resistance R... arc The model can be constructed based on existing common cybernetics arc models, which will not be elaborated here. Grounding resistance R c The physical model is a hemispherical conductive shell radiating from the arc source to infinity. Based on the grounding resistance R... c The physical model, grounding resistance R c The total resistance can be obtained by integrating a series of differential hemispherical shell resistors with thickness dr in series, as shown in equation (4).

[0093] (4)

[0094] In the formula, R is the arc radius, and r is the divergence radius.

[0095] Step 2: Conduct experiments on the target soil medium and fit the ionic conductivity ∑|z based on the experimental data. i |C i μ i The relationship between the fault current I and the current dissipation radius r is shown in the following formula:

[0096] Step 21: Obtain the curve of red soil resistivity as a function of electric field strength through a full-scale experiment. Under specific ambient temperature and soil moisture content, multiple repeated current impact tests were conducted to obtain the curve of soil resistivity ρ as a function of electric field strength E in the red soil medium, as shown below. Figure 4 As shown, ρ decreases non-linearly with increasing E, and the relationship between the two conforms to the law of an exponential function:

[0097] (5)

[0098] In the formula, ρ0 is the initial resistivity of the soil, and K is a constant. Further based on... Figure 4 The variation curve can be fitted to obtain the values ​​of K and ρ0 in equation (5), which are 0.0002071 and 897.23, respectively.

[0099] It should be noted that this embodiment takes red soil medium as an example. However, in actual applications, the above formula 5 still has general applicability under different scenarios / backgrounds of high-resistance grounding faults (HIF) and under different soil media. The difference is that the parameters are different for different soil media, such as ρ0.

[0100] Step 22, combining the relationship between electric field strength E and divergence radius r, E=Iρ / (2πr) 2 Substituting equation (3) into equation (5), we obtain the transcendental equation for ionic conductivity:

[0101] (6)

[0102] In the formula, I is the fault current (arc current).

[0103] Based on Equation 6, the ionic conductivity ∑|z i |C i μ i There is a correlation between the fault current I and the dissipation radius r. In order to analyze Formula 4, this invention performs step 23.

[0104] Step 23: By fitting a three-dimensional surface, establish a display relationship between the dielectric ionic conductivity and the fault current and the dispersion radius.

[0105] In this embodiment, the divergence radius r is taken every 0.1m from 0.1m to 10m, and the arc current I is taken every 0.1A from 0.1A to 10A, generating 10,000 sets of raw data (the ionic conductivity ∑|z is fitted according to equation (6)). i |C i μ i Then, the original data is fitted to obtain a three-dimensional fitted surface, such as... Figure 5 As shown. The ∑|z is obtained through mathematical fitting. i |C i μ i The optimal relational expression between r and I is:

[0106] (7)

[0107] In the formula, p1, p2, p3, p4 and p5 are fitting parameters of the soil medium. They are essentially medium characteristic quantities obtained by fitting the current impact test data. If the soil medium type is different, its soil conductivity is different, and the values ​​of the above five parameters will also be different.

[0108] Similarly, this embodiment takes red soil medium as an example. However, in practical applications, the above formula 7 still has general applicability under different scenarios / backgrounds of high-resistance grounding faults (HIF) and different soil media. The difference is that the parameters of different soil media are different, such as p1, p2, p3, p4 and p5.

[0109] Step 3: Substitute the displayed relationship into the grounding resistance integral model to obtain the analytical model of grounding resistance for the target soil medium. Specifically, substitute equation (7) into the grounding resistance integral formula of equation (4) to solve for R. c :

[0110] (8)

[0111] After considering the polarity characteristics of the AC signal and the grounding resistance, the final result is R. c for:

[0112] (9)

[0113] Similarly, Formula 9 has a certain degree of universality because the relationship between soil resistivity and electric field strength follows a fixed pattern, exhibiting an exponential function. Therefore, in practical applications, when dealing with different soil media, the model of Formula 9 can be directly introduced, and then the parameters p1, p2, p3, p4, and p5 corresponding to the current soil medium can be substituted to achieve real-time detection of grounding resistance.

[0114] From 32 data segments obtained from the actual test field, four sets of A-phase grounding fault test waveforms were selected, showing the distribution line grounded through typical media: red soil, fine sand, yellow soil, and sandy soil. The simulation parameters of the grounding resistance model for different media are shown in Table 1. Although the simulation parameter values ​​differ for different media types, they all conform to the unified physical laws of soil ion ionization, and the model framework has a certain degree of universality.

[0115] Table 1. Simulation parameters of grounding resistance models for different media

[0116] Resistance model simulation parameters Red soil fine sand Loess soil sand K 0.0002071 0.0003413 0.0002066 0.0002372 <![CDATA[ρ0]]> 897.2318 226.0016 500.6960 1496.3388 <![CDATA[p1]]> 395.7680 73.4387 199.7776 653.4641 <![CDATA[p2]]> -74.5327 -28.2103 -51.2467 -109.4265 <![CDATA[p3]]> 526.7333 156.3538 311.2398 907.2861 <![CDATA[p4]]> 75.2335 28.4085 51.6740 109.6536 <![CDATA[p5]]> -0.1898 -0.0809 -0.1152 -0.2942

[0117] Build in PSCAD Figure 2 The novel power distribution network simulation model shown is based on the HIF physical analysis process, combining a control theory arc resistance model and a grounding resistance model in series. The simulation parameters for red soil are set as p1=395.7680, p2=-74.5327, p3=526.7333, p4=75.2335, and p5=-0.1898. The waveforms of fault current voltage, arc resistance, and grounding resistance over time under red soil conditions are obtained as follows: Figures 6a-6d As shown, where, Figure 6a The fault current waveform is shown. Figure 6b This is the fault voltage waveform. Figure 6c This is the waveform of the arc resistance. Figure 6d This is the waveform of the grounding resistance.

[0118] It is evident that the fault current waveform exhibits a significant nonlinear "zero-crossing" distortion near the zero-crossing point, consistent with the dynamic physical process of HIF. The nonlinearity of both arc resistance and grounding resistance manifests as an increase in resistance during the "zero-crossing" period: near the zero-crossing point, the low system voltage prevents the air gap from breaking down, causing the arc resistance to become high due to increased dielectric recovery strength; simultaneously, the low fault voltage weakens the electric field strength generated by the current injected into the ground, thus increasing soil resistivity and reducing the conductivity of the fault current dissipation path, resulting in the grounding resistance reaching its peak value. Both the arc resistance and grounding resistance (Figure 6) reach a high-resistance state at this time, and their superposition ultimately forms the following pattern: Figure 7 The fault resistance waveform is shown. The superposition process is essentially a linear series, but because the waveform components of both the arc resistance and grounding resistance change nonlinearly with time, it exhibits an overall nonlinear characteristic. The total fault resistance R... F (t) = R arc (t) + R c (t).

[0119] Comparison of HIF real-world test waveforms and simulation waveforms under different grounding media, for example Figures 8a-8d As shown, Figure 8a Corresponding to red soil, Figure 8b Corresponding to fine sand, Figure 8c Corresponding to loess soil, Figure 8d For sandy soil, calculations showed that the similarity between the actual and simulated waveforms was above 0.997 for all four grounding media. Therefore, the model can be directly applied to areas with media compositions similar to the selected red soil, fine sand, yellow soil, and sandy soil types. For areas with significant differences, it is recommended to recalibrate key parameters through localized experiments. Furthermore, among the four grounding media, fine sand has the largest porosity and contains the most water. Under applied voltage, water promotes ionization, generating more ions and increasing the solution's conductivity. This results in the lowest fault resistance for grounding via fine sand compared to other media, and the simulation and experimental results are consistent with the theoretical analysis.

[0120] In summary, the fault model constructed in this invention can accurately describe the dynamic physical characteristics of HIF under different grounding media, which is consistent with the actual HIF operating conditions and has strong practicality.

[0121] In some embodiments, the present invention provides a method for detecting high-resistivity fault grounding resistance considering dielectric ion migration, comprising:

[0122] An analytical model of grounding resistance is constructed using the modeling method described in the above embodiments;

[0123] The grounding resistance detection results are obtained based on the analytical model of grounding resistance and the fault current at the time of detection, which are used to accurately characterize the features of high-resistance grounding faults.

[0124] Accurate characterization of high-resistance grounding faults through grounding resistance detection results can improve the fault handling capabilities of the distribution network. For example, the more accurate the description of grounding fault characteristics, the lower the false alarm rate in fault detection.

[0125] In some embodiments, the present invention provides a computer terminal, comprising: one or more processors; and a memory storing one or more computer programs; wherein the processor invokes the computer programs to implement:

[0126] The steps of the above-mentioned high-resistivity fault grounding resistance modeling method considering dielectric ion migration or the steps of the above-mentioned high-resistivity fault grounding resistance detection method considering dielectric ion migration.

[0127] The processor can be a Central Processing Unit (CPU), but it can also be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor. The processor is used to execute relevant programs to implement the technical solutions provided in the embodiments of the present invention.

[0128] The memory can be implemented in the form of read-only memory (ROM), static storage device, dynamic storage device, or random access memory (RAM). The memory can store the operating system and other applications. When the technical solutions provided in the embodiments of this specification are implemented through software or firmware, the relevant program code is stored in the memory, and the processor calls the algorithm program of the methods described above in the embodiments of this invention.

[0129] The above embodiments are preferred embodiments of this application. Those skilled in the art can make various changes or improvements based on them. Without departing from the overall concept of this application, these changes or improvements should fall within the scope of protection claimed in this application.

Claims

1. A method for modeling high-resistivity fault grounding resistance considering dielectric ion migration, characterized in that: Includes the following steps: An integral model of grounding resistance is established based on the physical mechanism of ion electromigration in soil media. This model represents the grounding resistance of a high-resistance fault with respect to the ion conductivity ∑|z. i |C i The nonlinear integral expressions for μ and the divergence radius r, z i C represents the valence charge of the i-th type ion. i Let μ be the concentration of type i ions in the soil medium. i Let be the electromobility of the i-th type of ion; Experiments were conducted on the target soil medium, and the ionic conductivity ∑|z was fitted based on the experimental data. i |C i μ i The explicit relationship between fault current I and dissipation radius r; Substituting the explicit relational expression into the grounding resistance integral model yields the analytical model of grounding resistance for the target soil medium, which is an analytical expression of grounding resistance with respect to fault current I.

2. The method according to claim 1, characterized in that: The mathematical expression of the grounding resistance integral model is as follows: ； In the formula, R c For grounding resistance, The radius of the electric arc is denoted as .

3. The method according to claim 2, characterized in that: The construction process of the grounding resistance integral model includes: First, based on the theory of ion electromigration, a physical model of soil resistivity is established: Soil resistivity ρ is the sum of electric field strength and the total current density of ions in the soil medium (J). c The ratio of to is used to characterize the soil medium's ability to impede electric current; the total current density of ions J c It is obtained by summing the products of the electromigration flux and the valence charge number of each ion, satisfying: , where J i Let E be the electromigration flux of the i-th type ion, and E be the electric field strength. Secondly, based on the grounding resistance R under a high-resistance grounding fault (HIF) c The physical model uses soil resistivity ρ to characterize grounding resistance R. c Nonlinearity; Among them, the grounding resistance R c The physical model refers to a hemispherical conductive shell radiating from the arc point source to infinity. Based on this hemispherical conductive shell, the grounding resistance R... c The total resistance is obtained by integrating a series of differential hemispherical shell resistances of thickness dr. The resulting integral model of the grounding resistance is expressed as: .

4. The method according to claim 1, characterized in that: Ionic conductivity ∑|z i |C i μ i The explicit relationship between the fault current I and the divergence radius r is based on the ionic conductivity ∑|z i |C i μ i The optimal relationship expression is derived by fitting experimental data and is related to the fault current I and the current dissipation radius r. The ionic conductivity ∑|z i |C i μ i The correlation between the fault current I and the current dissipation radius r is obtained as follows: Repeated current impact tests were conducted on the target soil medium to obtain the curve of soil resistivity ρ as a function of electric field strength E, and then the relationship between soil resistivity ρ and electric field strength E was fitted. Based on the relationship between electric field strength E and divergence radius r: E=Iρ / (2πr) 2 The relationship between soil resistivity ρ and electric field strength E, along with a physical model of soil resistivity based on ion electromigration theory, leads to a mathematical model of the correlation. The physical model for the soil resistivity is expressed mathematically as follows: J c The total current density of the soil medium.

5. The method according to claim 1, characterized in that: Used to fit the ionic conductivity ∑|z i |C i μ i The experimental data showing the relationship between the fault current I and the spill radius r were obtained by taking multiple values ​​of the spill radius r and the fault current I during the current impulse test.

6. The method according to claim 1, characterized in that: The analytical model for the grounding resistance is: ； In the formula, R c p1 represents the grounding resistance, and p2, p3, p4, and p5 are fitting parameters for the soil medium.

7. The method according to claim 6, characterized in that: Fitted ionic conductivity ∑|z i |C i μ i The relationship between the fault current I and the current dissipation radius r is as follows: ； In the formula, e is the natural base.

8. A method for detecting high-resistivity fault grounding resistance considering dielectric ion migration, characterized in that: An analytical model of grounding resistance is constructed using the method described in any one of claims 1-7; The grounding resistance detection results are obtained based on the analytical model of grounding resistance and the fault current at the time of detection.

9. A computer terminal, characterized in that: include: One or more processors; And a memory that stores one or more computer programs; The processor invokes a computer program to achieve the following: The steps of the high-resistivity fault grounding resistance modeling method considering dielectric ion migration as described in any one of claims 1-7, or the steps of the high-resistivity fault grounding resistance detection method considering dielectric ion migration as described in claim 8.

10. A power distribution network system, characterized in that: The power distribution network system, used for conducting realistic tests on target soil media, includes: Low-voltage power supply: used to provide power; Step-up transformer: The low-voltage side of the step-up transformer is connected to the low-voltage power supply to boost the voltage of the low-voltage power supply to the high voltage level required for the full-scale test; Busbar: Connected to the high-voltage side of the step-up transformer and serving as the power distribution hub, receiving high-voltage electricity from the step-up transformer and distributing it to the test circuit; Grounding conductor: As the high-voltage electrode of the test circuit, one end is connected to the busbar and the other end is laid on the target soil medium to form a current channel to simulate a high-resistance grounding fault. Signal detection equipment: including current transformers and voltage transformers, used to accurately measure the fault current flowing into the target soil medium and the fault voltage applied to the target soil medium; Insulators: live parts of busbars and grounding conductors that are fixed and supported in the test site to ensure safe electrical isolation from the ground and surrounding objects; The test data from the full-scale test of the power distribution network system are used to fit the explicit relationship in the method of any one of claims 1-7.

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