A lightning protection design method for grounding system of high-altitude mountain prefabricated cabin substation

Abstract

The present application relates to the technical field of lightning protection of power system, and aims to solve the problems that the soil resistivity is high and unevenly distributed in high-altitude mountainous areas, the traditional grounding grid design is based on a uniform soil model, which leads to a large deviation between the calculated value and the measured value of grounding resistance, the grounding system has insufficient discharge capacity and cannot meet the lightning protection safety threshold requirement, the traditional grounding system is not suitable for the special lightning characteristics of high-altitude mountainous areas, and a large amount of resistance-reducing agents are used to damage the environment, and provides a lightning protection design method for grounding system of prefabricated cabin substation in high-altitude mountainous areas, which comprises the following steps: step 1, data collection and summarization; step 2, modeling and visual analysis of the magnetic field in the prefabricated cabin; step 3, multi-layer soil modeling and performance index calculation; step 4, establishment of a comprehensive evaluation system, multi-dimensional evaluation of the design scheme, and obtaining of a prefabricated cabin lightning protection green safety design index. The present application improves the scientificity and safety of the lightning protection design of the prefabricated cabin through comprehensive data collection, accurate modeling analysis and multi-dimensional evaluation, and takes into account the environmental protection requirement.

Description

Technical Field

[0001] This invention relates to the field of power system lightning protection technology, and in particular to a lightning protection design method for a grounding system of a prefabricated substation in a high-altitude mountainous area. Background Technology

[0002] Prefabricated substations are substations where the main transformer and high-voltage power distribution equipment are located outdoors or inside prefabricated cabins, while medium-voltage power distribution equipment and secondary equipment are prefabricated inside the cabins. Design, assembly, wiring, and commissioning are completed in the factory, and modular installation is carried out on-site. As an emerging construction model, prefabricated substations are gradually becoming an important direction in substation construction due to their advantages such as short construction time, small footprint, and minimal environmental impact.

[0003] The reliable operation of the power system in a prefabricated substation and the safety of equipment and personnel within the station are closely related to the effectiveness of the grounding system in the prefabricated substation.

[0004] When deploying prefabricated substations in high-altitude mountainous areas (where high altitude refers to altitudes above 1000m), the complex terrain and unstable geological structure of these areas, along with frequent geological disasters such as earthquakes, landslides, debris flows, and permafrost thawing, increase the difficulty of substation site selection and construction, and pose a serious threat to the stability of the prefabricated substation's grounding system. Due to the variable geological conditions and complex soil structure, resistivity often exhibits significant differences. Traditional grounding systems struggle to guarantee the stability and effectiveness of grounding resistance under these complex geological conditions, potentially leading to equipment damage and personnel safety accidents.

[0005] The unique geographical and climatic conditions in mountainous areas result in lightning currents characterized by large amplitude, high frequency, and high steepness. When a lightning current with a large amplitude strikes a substation, it releases enormous energy, and the instantaneous high temperature and strong electromagnetic force can easily damage the equipment inside the substation. The high frequency of lightning activity significantly increases the probability of a substation being struck by lightning, placing equipment in a dangerous environment for a long time, accelerating equipment aging and increasing the frequency of failures. The high steepness of the lightning current can induce strong electromagnetic induction, interfering with the normal operation of electronic equipment and seriously threatening the safety and stability of the power system.

[0006] In addition, due to the compact structure and limited internal space of prefabricated substations, lightning protection design is extremely difficult in high-altitude mountainous areas. Traditional large-scale lightning protection facilities are difficult to install, and the layout of the grounding system is also greatly restricted, making it difficult to build a complete lightning protection system in the conventional way.

[0007] Therefore, designing lightning protection for the grounding system of prefabricated substations to adapt to the special environment of high-altitude mountainous areas and effectively mitigate the threat of lightning currents with large amplitude, high frequency, and high steepness has become the core key to ensuring the safe operation of substations.

[0008] Currently, the design of grounding grids for prefabricated substations still commonly relies on simple empirical formulas recommended by various standards and specifications for approximate calculations. While this method is conceptually clear and easy to use, its applicability is significantly limited. Especially in high-altitude mountainous areas, traditional grounding grid design methods face multiple severe challenges: 1. High soil resistivity and complex geological conditions; The geological conditions in high-altitude mountainous areas are extremely complex, with soil structures exhibiting significant heterogeneity and stratification. Field measurements show that soil resistivity in these areas generally ranges from 500 Ω·m to 3000 Ω·m, reaching over 5000 Ω·m in some bedrock areas. Furthermore, vertical stratification is significant, and horizontal distribution is uneven. Traditional grounding grid designs typically employ a uniform soil model, neglecting the variations in soil resistivity in both horizontal and vertical directions. This leads to significant discrepancies between the calculated grounding resistance and the measured resistance, seriously threatening the reliability of the grounding system.

[0009] 2. High-altitude mountainous areas exhibit unique characteristics in lightning activity; Current lightning protection designs generally adopt a fixed lightning current parameter system (such as 100kA peak current, 8 / 20μs standard waveform). Its theoretical framework is based on the basic assumption that lightning parameters follow a static probability distribution. However, the actual lightning current amplitude follows a log-normal distribution (IEEE Std 1410), resulting in over-design or under-protection in many scenarios.

[0010] Lightning currents in high-altitude areas are characterized by large amplitude (up to 287kA in actual measurements), high steepness (10 / 350μs waveforms account for 35%), and high frequency (more than 70 thunderstorm days per year). More seriously, the cumulative effect caused by high-frequency lightning strikes can lead to accelerated corrosion of grounding materials.

[0011] Conventional lightning protection design methods do not fully consider the special geographical and climatic factors of the region and cannot effectively cope with the complex and ever-changing lightning strike risks. This makes high-altitude mountain prefabricated substations face a high risk of lightning strike accidents during operation.

[0012] Lightning activity in high-altitude mountainous areas has unique characteristics, and traditional modeling methods have serious limitations. There is an urgent need to construct a dynamic probabilistic model based on regional lightning characteristic parameters and further establish a multi-dimensional evaluation index system for lightning protection reliability.

[0013] Although the literature “Zhao Jie. Research on reducing the grounding resistance of substations with high soil resistivity, Water Resources and Hydropower Technology and Application, 2024, 6(3): 37-39” and “Cao Jianshe. Design of grounding grid of main substation in high soil resistivity area based on CDEGS software, Urban Rail Transit Research, 2024, 27(7): 328-331” have carried out optimization research on the grounding system design of substations in high soil resistivity areas, neither of them has incorporated the distribution of dynamic lightning parameters into the system analysis framework, which leads to limited engineering applicability.

[0014] 3. The conflict between environmental constraints and project implementation is becoming increasingly prominent; High-altitude ecosystems are fragile. Traditional large-scale grounding grid construction requires excavating thousands of square meters of area, which damages local vegetation and ecological environment. Furthermore, the extensive use of resistance-reducing agents in grounding equipment can pollute groundwater resources and cause a series of environmental problems such as reduced biodiversity.

[0015] Prefabricated substations, constrained by their compact layout design, have severely limited space for grounding grid expansion. Coupled with stringent environmental regulations restricting the use of chemical resistance-reducing agents, these dual constraints lead to widespread grounding resistance exceeding standards in high soil resistivity areas under existing technological systems, seriously threatening the safe operation of the power system. Chinese invention patent application CN201810954562.8 discloses a design method for prefabricated concrete grounding grids. While its proposed modular assembly design for prefabricated substation grounding grids can shorten the construction cycle, its applicability is limited to geologically stable areas and is not suitable for high-altitude mountainous regions. The substation optimization scheme in the literature "Jin Qingqing, Chen Tao. Research on Lightning Protection and Grounding Device Design of Substations, Automation Application, 2024, 65(24A): 62-64, 67" is limited by the assumption of a low resistivity environment and cannot solve the technical challenges under the special geological conditions of high-altitude mountainous areas.

[0016] To address the issues of high resistivity and stratification in high-altitude mountain soils, it is urgent to break through the traditional uniform model framework, introduce a refined stratified modeling method, and construct a multi-layered soil computational model that conforms to actual geological characteristics.

[0017] Based on the above problems, there is an urgent need to propose a lightning protection design method for the grounding system of prefabricated substations in high-altitude mountainous areas. This method aims to solve the design challenges of grounding systems under multiple special conditions, such as high soil resistivity, special lightning characteristics, and environmental constraints in high-altitude mountainous areas, thereby ensuring the safe operation of power infrastructure and protecting the ecological environment. Summary of the Invention

[0018] This invention aims to provide a lightning protection design method for the grounding system of a prefabricated substation in a high-altitude mountainous area. This method addresses the problems of high and uneven soil resistivity in high-altitude mountainous regions, the large deviation between calculated and measured grounding resistance values ​​caused by traditional grounding grid designs based on uniform soil models, insufficient current discharge capacity of the grounding system, inability to meet lightning protection safety threshold requirements, incompatibility of traditional grounding systems with the special lightning characteristics of high-altitude mountainous areas, and the potential damage to the ecological environment from the extensive use of resistance-reducing agents.

[0019] This invention is achieved using the following technical solution: This invention provides a lightning protection design method for the grounding system of a prefabricated substation in a high-altitude mountainous area, comprising the following steps: Step 1: Data collection and summarization; Step 2: Model the magnetic field inside the prefabricated cabin and perform visualization analysis; Step 3: Multi-layer soil modeling and performance index calculation; Step 4: Establish a comprehensive evaluation system, evaluate the design scheme from multiple dimensions, and obtain the green safety design index for prefabricated cabin lightning protection.

[0020] As a preferred technical solution: Step 1 specifically includes: collecting data, conducting geological exploration based on the actual engineering situation, collecting and summarizing relevant data, including prefabricated cabin size data, automated screen size data, soil resistivity, soil moisture content, design data, historical lightning strike data, and environmental protection data.

[0021] As a preferred technical solution: In step 1, the soil resistivity was measured using the Winner four-electrode method. Four electrodes were arranged at equal intervals along a straight line, with a spacing of [missing information]. a The depth to which each electrode is driven into the ground is... b Soil resistivity The calculation formula is:

[0022] Where R is the measuring resistance.

[0023] As a preferred technical solution: Step 1 also includes modeling the lightning current by constructing a probability density function of the lightning current amplitude based on historical lightning strike data, according to the following formula:

[0024] in, This represents the peak value of the lightning current, expressed in kA. This is the mean of the logarithms of the peak lightning current; denoted as the standard deviation of the logarithm of the peak lightning current.

[0025] As a preferred technical solution: Step 2 specifically includes the following steps: Step 2.1: Model the magnetic field between LPZ1 and LPZ2 inside the prefabricated cabin; Step 2.2: Model the magnetic field inside LPZ2 in the prefabricated cabin; Step 2.3: Import the prefabricated cabin size data, automated screen size data, design data, and historical lightning strike data obtained in Step 1 into the magnetic field strength model established in Steps 2.1 and 2.2 to generate a visualization result of the magnetic field distribution inside the prefabricated cabin; optimize the grid density of the prefabricated cabin shielding layer by analyzing the spectral characteristics of different lightning strike waveforms.

[0026] As a preferred technical solution: In step S2.1, the magnetic field between LPZ1 and LPZ2 inside the prefabricated cabin is modeled, and the specific formula is as follows:

[0027] in: The shortest distance between the automated control cabinet and the roof of the prefabricated cabin, in units of... m ; The shortest distance between the automated control cabinet and the prefabricated cabin door panel, in units of... m ; Time-varying lightning current, unit: A ; The structural coefficient is set to 0.01. The width of the prefabricated cabin shielding mesh, in units of m ; The harmonic frequency of the lightning strike current, in units of . MHz .

[0028] As a preferred technical solution: Step 2.2 involves modeling the magnetic field inside LPZ2 within the prefabricated cabin. The specific formula is as follows:

[0029] in, The shielding coefficient is calculated using the following formula:

[0030] in: The grid width for the grid-type spatial shielding, in units of m ; The radius of the grid-type shielded conductor, in units of m ; Lightning strike density, measured in strikes per second. km ² / year.

[0031] As a preferred technical solution: Step 3 specifically includes the following steps: Step 3.1: The measurement area is divided into zones using the K-means clustering algorithm. Based on the soil resistivity data obtained in Step 1, a multi-layer soil model is established using the least squares method. Sum of squared errors function Defined as:

[0032] in, It is the first The resistivity measured this time. It is the first The depth measured in this measurement These are model predictions. The parameter vector to be determined; right Regarding each parameter separately ( Find the partial derivatives and set them equal to 0 to obtain the system of equations: =0 Solving this equation yields the vector. Relationship with function ; Using the coefficient of determination To evaluate the accuracy of the modeling, ; in, It is the average of the measured values; Step 3.2: Apply the obtained multi-layer soil model to the grounding system design, and calculate the grounding system performance indicators based on the soil model. The grounding system performance indicators include grounding resistance, contact voltage, step voltage, and grounding short-circuit current. Step 3.3: Dynamically adjust the length of the grounding conductor based on the regional lightning strike density. The length of the grounding conductor is:

[0033] in, This is a correction factor for geological type; The average soil resistivity; This refers to the density of lightning strikes.

[0034] As a preferred technical solution: Step 3.2 involves calculating the performance indicators of the grounding system, including: Calculate the grounding resistance of the horizontal grounding grid and grounding resistance of deep well grounding electrode The calculation formula is:

[0035]

[0036] Where, constant ;constant ; The area of ​​the horizontal grounding grid is expressed in units of... ; The diameter or equivalent diameter of the horizontal grounding electrode, in units of m ; The burial depth of the horizontal grounding electrode, in units of m ; The total length of the outer edge of the grounding grid, in units of m ; The total length of the horizontal grounding electrode, in units of m ; Soil resistivity, unit: ; Calculate contact voltage Step voltage and target grounding resistance The calculation formula is:

[0037]

[0038]

[0039] in, The total time for the short-circuit current to flow, in units of s ; The resistivity of the ground soil at the position where a person is standing; The soil attenuation coefficient; Frequency-related factors; The formula for calculating the short-circuit current to ground after a lightning strike is as follows:

[0040] in, This refers to the maximum short-circuit fault current of the substation as specified in the design specifications. This is the diversion coefficient; This is the attenuation coefficient.

[0041] As a preferred technical solution: Step 4 specifically includes the following steps: Step 4.1: Evaluate the lightning protection effect and obtain a safety score; Step 4.2: Environmental performance evaluation, obtaining an environmental performance score; Step 4.3: Based on the evaluation results from various dimensions, the prefabricated cabin lightning protection green safety design index is obtained. Environmental rating+ Safety rating; in, As a weighting factor in the environmental rating, The weights for the security score, and .

[0042] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. This invention innovates and improves upon traditional lightning protection design methods in multiple dimensions. In soil resistivity modeling, it employs K-means clustering to intelligently partition the measurement area and establishes an accurate mathematical model of soil resistivity for each area using the least squares method. This significantly improves the calculation accuracy of soil resistivity, reduces the deviation between calculated and measured grounding resistance values, and ensures that the grounding system's discharge capacity meets the lightning protection safety threshold requirements. In lightning current characteristic modeling, it introduces a time-varying parameter model (time-varying lightning current), overcoming the limitations of using fixed lightning current parameters in traditional designs. This allows the grounding system design to adapt to the special lightning characteristics of high-altitude mountainous areas. This invention achieves adaptive optimization of lightning protection system parameter design, providing a more accurate and reliable design method for lightning protection in complex environments. By integrating accurate soil resistivity modeling and dynamic lightning current characteristic analysis, this invention achieves automated calculation and optimization design of multiple grounding network parameters (i.e., performance indicators of each grounding system). This invention can quickly calculate the lightning protection green safety design index, offering advantages such as high speed, high accuracy, and simple parameter changes. The conclusions obtained can provide support and guidance for lightning protection design optimization in high-altitude mountainous areas. This invention takes environmental protection into account in the calculation of the green safety design index for lightning protection of prefabricated cabins, thus avoiding the problem of damaging the ecological environment by using large amounts of drag-reducing agents.

[0043] 2. This invention addresses the challenges of lightning protection design in high-altitude, mountainous, and high-resistivity geographical environments. It focuses on overcoming the technical bottlenecks in protection under the coupled effects of high resistivity geological features and complex lightning activity. Through a research method combining theoretical modeling, computer simulation, and field testing, it successfully overcomes the technical pain points of traditional solutions in high-altitude areas, such as excessive grounding resistance and delayed lightning impulse response. The research results have been successfully applied in lightning protection upgrade projects of several substations in the mountainous areas of Sichuan. Measured grounding resistance values ​​and lightning strike rates have significantly decreased compared to traditional solutions, providing a reliable technical solution for lightning protection of power facilities in high-altitude and special regions.

[0044] 3. This invention improves the scientificity and safety of prefabricated cabin lightning protection design by comprehensively collecting data, accurately modeling and analyzing, and evaluating from multiple dimensions, while also taking into account environmental protection requirements. Attached Figure Description

[0045] Figure 1 This is a schematic diagram showing the division of lightning protection zones in a prefabricated substation. Figure 2 This is a schematic diagram of the substation's current distribution; Figure 3 This is a flowchart of the lightning protection design method for the grounding system of a prefabricated substation in a high-altitude mountainous area, as described in this invention. Figure 4 This is a diagram showing the magnetic field distribution within LPZ2 in the embodiment; Figure 5 This is a layered soil fitting diagram obtained after modeling using the least squares method in the embodiment. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] Example 1 like Figure 3 As shown in the figure, this embodiment proposes a lightning protection design method for the grounding system of a prefabricated substation in a high-altitude mountainous area, including the following steps: Step 1: Data collection and summarization; Step 1 specifically includes: collecting data, conducting geological exploration based on the actual engineering situation, collecting and summarizing relevant data, including prefabricated cabin size data, automated screen size data, soil resistivity, soil moisture content, design data, historical lightning strike data, environmental protection data, etc.

[0048] In step 1, the soil resistivity was measured using the Winner four-electrode method. Four electrodes were arranged at equal intervals along a straight line, with a spacing of [missing information]. a The depth to which each electrode is driven into the ground is... b Soil resistivity The calculation formula is:

[0049] Where R is the measuring resistance.

[0050] Within the selected measurement area, the soil resistivity is measured vertically downwards at regular intervals (e.g., 0.1 meters, 0.2 meters, etc.), and the corresponding depth and measurement value are recorded.

[0051] Data from multiple measurements at various locations are recorded as follows: ,in Indicates the first The depth measured in this measurement This indicates the corresponding soil resistivity.

[0052] Based on historical lightning strike data (i.e., historical lightning strike data for the area where the prefabricated substation is located), the lightning current amplitude probability density function is constructed according to the following formula to model the lightning current:

[0053] in, This represents the peak value of the lightning current, expressed in kA. This is the mean of the logarithms of the peak lightning current; denoted as the standard deviation of the logarithm of the peak lightning current.

[0054] Step 2: Model the magnetic field inside the prefabricated cabin and perform visualization analysis; Step 2 specifically includes the following steps: Step 2.1: Model the magnetic field between LPZ1 and LPZ2 inside the prefabricated cabin. The specific formula is as follows:

[0055] in: The shortest distance between the automated control cabinet and the roof of the prefabricated cabin, in units of... m ; The shortest distance between the automated control cabinet and the prefabricated cabin door panel, in units of... m ; The current is a time-varying lightning current (8 / 20μs or 10 / 350μs waveform), and the unit is... A The time-varying lightning current model is derived from historical lightning strike data of the area where the prefabricated substation is located. The structural coefficient is set to 0.01. The width of the prefabricated cabin shielding mesh, in units of m ; The harmonic frequency of the lightning strike current, in units of . MHz ; LPZ1 refers to the first lightning protection zone, and LPZ2 refers to the second lightning protection zone, which is located inside LPZ1. Figure 1 As shown, the yellow markings represent lightning; the substation's shunt design is as follows: Figure 2 As shown.

[0056] Step 2.2: Model the magnetic field inside LPZ2 in the prefabricated cabin. The specific formula is as follows:

[0057] in, The shielding coefficient is calculated using the following formula:

[0058] in: The grid width for the grid-type spatial shielding, in units of m; The radius of the grid-type shielded conductor, in units of m ; Lightning strike density, measured in strikes per second. km ² / year.

[0059] Step 2.3: Import the prefabricated cabin size data, automated screen size data, design data, historical lightning strike data, etc. obtained in Step 1 into the magnetic field strength model established in Step 2.1 and Step 2.2 to generate a visualization result of the magnetic field distribution inside the prefabricated cabin (e.g., in the form of an image). Fast Fourier Transform (FFT) was performed on the lightning current waveform to obtain the statistical spectral characteristics of regional lightning. By analyzing the spectral characteristics of different lightning waveforms, the grid density of the prefabricated substation shielding layer was optimized. The grounding system of the prefabricated substation was designed according to the probability density function of lightning current amplitude in different regions. P ( I Based on the frequency and waveform characteristics of lightning strikes, the shielding mesh density is adaptively adjusted to ensure that the magnetic field strength inside the chamber always meets the design requirements. The adjustment strategy is as follows: 1) Areas with high lightning strike frequency ( (≥10 times / km² / year), using a compact shielding mesh, reducing the radius of the shielding conductor, and increasing the mesh density. 1) No more than 0.1m; 2) Low to medium lightning frequency areas ( <10 times / km² / year), using standard shielding mesh. Less than 0.5m.

[0060] Electromagnetic pulses caused by lightning currents can be fatal to equipment inside substations. Traditional design standards and technologies only consider the case where the lightning current magnitude is constant, ignoring the wide spectrum characteristics of lightning currents and the impact of different lightning strike frequencies on equipment. This invention models the magnetic field between LPZ1 and LPZ2 and the magnetic field within LPZ2 in a prefabricated substation, fully considering the influence of lightning current magnitude and lightning strike frequency, and establishes a dynamic magnetic field strength model. In practice, the calculation results from steps 2.1 and 2.2 (which can be generated as follows) can be used to... Figure 4 The visualization results shown indicate that by adjusting the grid density of the prefabricated cabin's shielding layer and the radius of the shielding conductor, the magnetic field strength inside the cabin can be controlled within the design specifications.

[0061] Step 3: Multi-layer soil modeling and performance index calculation; Step 3 specifically includes the following steps: Step 3.1: Use the K-means clustering algorithm to intelligently partition the measurement area. Based on the soil resistivity and other data obtained in Step 1, use the least squares method to establish a multi-layer soil model. Assuming soil resistivity With depth There is a certain functional relationship between them. ,in It is the parameter vector to be determined.

[0062] For each measurement data point The model predicts the value. Then the error at that point is = .

[0063] The goal of the least squares method is to minimize the sum of squared errors at all measurement points, i.e., to minimize the error sum of squares function. The error sum of squares function... Defined as:

[0064] in, It is the first The resistivity measured this time. It is the first The depth measured in this measurement These are model predictions. The parameter vector to be determined.

[0065] In order to find Minimum vector ,right Regarding each parameter separately ( Find the partial derivatives and set them equal to 0 to obtain a system of equations: =0 Solving this equation yields the vector. Relationship with functions.

[0066] Using the coefficient of determination To evaluate the accuracy of the modeling, .

[0067] in, It is the average of the measured values. The value of is between 0 and 1, and the closer it is to 1, the better the fit.

[0068] If the soil has many layers and is complex, professional computer analysis software (such as CDEGS software) can be used to perform layer-by-layer modeling and calculation of the measured soil resistivity in order to obtain a multi-layer soil model that is closest to reality.

[0069] Step 3.2: Apply the obtained multi-layer soil model to the grounding system design, and calculate the grounding system performance indicators based on the soil model: grounding resistance, contact voltage, step voltage, and grounding short-circuit current, etc. Calculate the grounding resistance of the horizontal grounding grid and grounding resistance of deep well grounding electrode The calculation formula is:

[0070]

[0071] Where, constant ;constant ; The area of ​​the horizontal grounding grid is expressed in units of... ; The diameter or equivalent diameter of the horizontal grounding electrode, in units of m ; The burial depth of the horizontal grounding electrode, in units of m ; This refers to the total length of the outer edge of the grounding grid, in meters. The total length of the horizontal grounding electrode, in units of m ; Soil resistivity, unit: .

[0072] Introducing correction coefficients Taking into account factors such as seasonal changes, the revised formula is:

[0073]

[0074] Calculate contact voltage Step voltage and target grounding resistance The calculation formula is:

[0075]

[0076]

[0077] in, The total time for the short-circuit current to flow, in units of s ; The resistivity of the ground soil at the position where a person is standing; The soil attenuation coefficient; This is a frequency-related factor.

[0078] Calculate the short-circuit current to ground after a lightning strike; First, calculate the zero-sequence current flowing through different locations on the ground wire of the overhead line. The calculation formula is:

[0079]

[0080] , The calculation formula is:

[0081]

[0082] in, e For natural index; β The propagation constant; s The total number of segments for the ground wire (i.e., the entire ground wire is divided into segments). s A uniform segment, typically corresponding to s +1 tower). n The current tower number being calculated ( n =1,2,..., s +1); R st The grounding resistance of the tower (i.e., the resistance value of each tower grounding device), in units of... Ω ; I b The total zero-sequence current injected into the ground wire (usually from the substation side or the fault point), in units of A ; j The imaginary unit; The ground impedance per unit length, in units of ; The mutual impedance per unit length between the phase conductor and the ground conductor, in units of . ; The average length of the gear spacing, in units of ; The ground wire reactance per unit length, in units of ; The radius of the ground wire, in units of ; The number of ground wires; The distance to the ground wire, in units of ; The geometric mean distance of the ground wire, in units of ; The mirror image distance of the ground wire to the ground, in units of .

[0083] Calculate the diversion coefficient The calculation formula is:

[0084] The formula for calculating the short-circuit current is as follows:

[0085] in, This refers to the maximum short-circuit fault current of the substation as specified in the design specifications. This is the diversion coefficient; This is the attenuation coefficient.

[0086] If the substation model is complex or if multiple lightning strikes have caused faults, professional computer analysis software (such as CDEGS) can be used to calculate the fault current distribution accurately.

[0087] Step 3.3: Dynamically adjust the length of the grounding conductor based on the regional lightning strike density. The length of the grounding conductor is:

[0088] in, This is a geological type correction factor (0.8 for clay, 1.2 for rock). The average soil resistivity; This refers to the density of lightning strikes.

[0089] Traditional design methods typically employ homogeneous soil models to estimate soil resistivity. However, in high-altitude mountainous regions, due to complex soil structures and varied geological conditions, resistivity often exhibits significant differences. In such cases, the simplistic assumptions of homogeneous soil models can lead to substantial errors. To address this, this invention proposes an improved soil modeling approach: First, K-means clustering is used to automatically classify measured resistivity data, determining the optimal number of soil layers for intelligent zoning. Then, the least squares method is used to inversely optimize the resistivity parameters of each soil layer, constructing a multi-layered soil model. Finally, the modeling accuracy is evaluated using the coefficient of determination (R²). This method not only overcomes the limitations of traditional homogeneous models but also more accurately reflects the distribution characteristics of soil resistivity in a given region, providing a reliable theoretical basis for engineering applications such as power system grounding design and lightning protection.

[0090] Step 4: Establish a comprehensive evaluation system, evaluate the design scheme from multiple dimensions, and obtain the green safety design index for prefabricated cabin lightning protection.

[0091] Step 4 specifically includes the following steps: Step 4.1: Lightning protection effectiveness evaluation. Based on indicators such as actual grounding resistance, target grounding resistance, contact voltage, step voltage, and grounding grid impulse response time, comprehensively evaluate the protection capability of the lightning protection system for the prefabricated cabin and its internal equipment. The safety score is 100 for the best safety and 0 for the worst safety.

[0092] Step 4.2: Environmental performance evaluation, considering factors such as whether the materials used are environmentally friendly and their impact on soil and the environment. The environmental performance score is 100 for the best results and 0 for the worst results.

[0093] Step 4.3: Based on the evaluation results from various dimensions, the prefabricated cabin lightning protection green safety design index is obtained. Environmental rating+ Security rating. Among them, As a weighting factor in the environmental rating, As the weight for the security score, and .

[0094] When the prefabricated cabin lightning protection green safety design index When the design scheme is approved; when Prefabricated cabin lightning protection green safety design index At that time, local optimization is required; when the prefabricated cabin lightning protection green safety design index At that time, a redesign is required.

[0095] Based on lightning strike density Automatically adjust evaluation weights. At that time, it is a high-risk area, and the safety weight accounts for 60%, reflecting the priority of safety; At that time, it was a low-risk area, with environmental protection accounting for 60% of the weight, reflecting the green priority.

[0096] This evaluation system employs a multi-dimensional weighted assessment model, based on design indicators and expert review opinions, to conduct a comprehensive quantitative evaluation of the scheme from multiple dimensions, including lightning protection effectiveness and environmental performance. Simultaneously, it automatically adjusts the evaluation weights according to lightning strike frequency and environmental indicators, adapting to different regions.

[0097] The following example uses a prefabricated module of a substation: The lightning protection design method for the grounding system of a prefabricated substation in a high-altitude mountainous area includes the following steps: Step 1: Data Collection. Based on the actual engineering conditions, conduct a detailed geological survey of the site, collect and summarize data, including prefabricated cabin size data (such as the width of the prefabricated cabin shielding mesh), automation screen size data, design data (such as the magnetic field strength in the main equipment room should not exceed the design value), measured soil resistivity and soil moisture content data, historical lightning strike data (including the frequency of lightning occurrence in different seasons and the magnitude of lightning current), and environmental data (such as electromagnetic radiation, noise, soil composition, air pollution index, etc.). All data are measured multiple times to ensure accuracy.

[0098] Step 2: Model the magnetic field between LPZ1 and LPZ2 and the magnetic field within LPZ2 in the prefabricated substation. The magnetic field distribution diagram within LPZ2 is shown below. Figure 4 As shown; Calculations show that when the lightning frequency... A compact shielding mesh is required. When the frequency of lightning strikes Standard shielding mesh can be used. 。 When the frequency and current of lightning strikes increase, a smaller honeycomb shielding structure is used. This embodiment represents a region with frequent lightning strikes; the actual equipment design parameters are as follows. After secondary shielding using a cabinet, the electromagnetic field strength is 131 A / m, which is lower than the design specification of 800 A / m for secondary equipment (mainly network and automation equipment). Furthermore, additional shielding design can be implemented for individual devices to meet the electromagnetic field strength requirements.

[0099] Step 3: The measurement area is intelligently partitioned using the K-means clustering algorithm, and multi-layer soil modeling is performed using the least squares method to calculate the grounding resistance. Based on the data and calculations, the soil in this area can be roughly divided into four layers. The fitting formula for the relationship between grounding resistance y and the measured soil depth x is as follows: Coefficient of determination The layered soil fitting diagram is as follows: Figure 5 As shown. Based on the calculated target grounding resistance. It was found that the actual soil grounding resistance at a depth of 2.8m was close to The initial grounding grid design used a horizontally spaced grounding grid with vertical grounding electrodes buried 2.8m underground. Calculations showed that the actual grounding resistance was approximately 4.33Ω, which did not meet the requirements. Therefore, the grounding grid needed to be extended by 17.8m in both length and width, and modified to a horizontally spaced grid with unequal spacing. Additionally, eight 50-meter-long inclined wells were drilled at the four corners of the grounding grid. Calculations showed that the actual grounding resistance was now approximately 1.02Ω. The minimum contact voltage was limited to 176V, and the maximum contact voltage was 113.492V < 176V. The minimum step voltage was limited to 208V, and the maximum step voltage was 176.548V < 208V. Both the contact voltage and step voltage met the requirements.

[0100] Step 4: Evaluate the design scheme in terms of lightning protection effectiveness and environmental performance. Expert review confirmed that the lightning protection effectiveness meets all requirements, and calculations also show that the results meet all design specifications, resulting in a safety score of 95. Furthermore, based on the design in Step 3.3, the amount of grounding material used is reduced by 14.53% compared to traditional methods, protecting the environment, resulting in an environmental performance score of 88. This area is a high-lightning-strike zone, therefore... Therefore, the total score is 92.2 points, and the design scheme is approved.

[0101] This method does not use grounding resistance as the sole criterion. Instead, it establishes a layered soil model to calculate grounding resistance and short-circuit current into the ground, while simultaneously calculating multiple parameters related to equipment magnetic field, contact voltage, step voltage, and environmental performance. Compared to traditional lightning protection designs that rely on fixed standards, this invention quantifies lightning strike risk into engineering parameters through mathematical modeling, enabling precise protection in high-lightning-rate and high-resistance areas. Practical application verification shows that this design method effectively improves the lightning protection performance of prefabricated enclosures, ensures the grounding grid performance meets design requirements, reduces costs, and protects the environment.

[0102] This invention innovates and improves upon traditional lightning protection design methods in multiple dimensions. In soil resistivity modeling, it employs K-means clustering to intelligently partition the measurement area and establishes an accurate mathematical model of soil resistivity for each area using the least squares method, significantly improving the calculation accuracy. In lightning current characteristic modeling, it introduces a time-varying parameter model, overcoming the limitations of using fixed lightning current parameters in traditional designs. This invention achieves adaptive optimization of lightning protection system parameter design, providing a more accurate and reliable design method for lightning protection in complex environments. By integrating accurate soil resistivity modeling with dynamic lightning current characteristic analysis, this invention achieves automated calculation and optimization design of multiple grounding grid parameters. It can quickly calculate the lightning protection green safety design index, offering advantages such as high speed, high accuracy, and simple parameter changes. The conclusions obtained can provide support and guidance for lightning protection design optimization in high-altitude mountainous areas.

[0103] This invention addresses the challenges of lightning protection design in high-altitude, mountainous, and high-resistivity geographical environments. It focuses on overcoming the technical bottlenecks in protection under the coupled effects of high resistivity geological features and complex lightning activity. Through a research method combining theoretical modeling, computer simulation, and field testing, it successfully overcomes the technical pain points of traditional solutions in high-altitude areas, such as excessive grounding resistance and delayed lightning impulse response. The research results have been successfully applied in lightning protection upgrade projects at several substations in the mountainous areas of Sichuan. Measured grounding resistance values ​​and lightning strike rates have significantly decreased compared to traditional solutions, providing a reliable technical solution for lightning protection of power facilities in high-altitude and special regions.

[0104] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A lightning protection design method for a grounding system of a prefabricated substation in a high-altitude mountainous area, characterized in that: Includes the following steps: Step 1: Data collection and summarization; Step 2: Model the magnetic field inside the prefabricated cabin and perform visualization analysis; Step 3: Multi-layer soil modeling and performance index calculation; Step 4: Establish a comprehensive evaluation system, evaluate the design scheme from multiple dimensions, and obtain the green safety design index for prefabricated cabin lightning protection.

2. The lightning protection design method for the grounding system of a prefabricated substation in a high-altitude mountainous area according to claim 1, characterized in that: Step 1 specifically includes: collecting data, conducting geological exploration based on the actual engineering situation, collecting and summarizing relevant data, including prefabricated cabin size data, automated screen size data, soil resistivity, soil moisture content, design data, historical lightning strike data, and environmental protection data.

3. The lightning protection design method for the grounding system of a prefabricated substation in a high-altitude mountainous area according to claim 2, characterized in that: In step 1, the soil resistivity was measured using the Winner four-electrode method. Four electrodes were arranged at equal intervals along a straight line, with a spacing of [missing information]. a The depth to which each electrode is driven into the ground is... b Soil resistivity The calculation formula is: Where R is the measuring resistance.

4. The lightning protection design method for the grounding system of a prefabricated substation in a high-altitude mountainous area according to claim 2, characterized in that: Step 1 also includes modeling the lightning current by constructing a probability density function of the lightning current amplitude based on historical lightning strike data, according to the following formula: in, This represents the peak value of the lightning current, expressed in kA. This is the mean of the logarithms of the peak lightning current; denoted as the standard deviation of the logarithm of the peak lightning current.

5. The lightning protection design method for the grounding system of a prefabricated substation in a high-altitude mountainous area according to claim 1, characterized in that: Step 2 specifically includes the following steps: Step 2.1: Model the magnetic field between LPZ1 and LPZ2 inside the prefabricated cabin; Step 2.2: Model the magnetic field inside LPZ2 in the prefabricated cabin; Step 2.3: Import the prefabricated cabin size data, automated screen size data, design data, and historical lightning strike data obtained in Step 1 into the magnetic field strength model established in Steps 2.1 and 2.2 to generate a visualization result of the magnetic field distribution inside the prefabricated cabin; optimize the grid density of the prefabricated cabin shielding layer by analyzing the spectral characteristics of different lightning strike waveforms.

6. The lightning protection design method for the grounding system of a prefabricated substation in a high-altitude mountainous area according to claim 5, characterized in that: In step S2.1, the magnetic field between LPZ1 and LPZ2 inside the prefabricated cabin is modeled, and the specific formula is as follows: in: The shortest distance between the automated control cabinet and the roof of the prefabricated cabin, in units of... m ; The shortest distance between the automated control cabinet and the prefabricated cabin door panel, in units of... m ; Time-varying lightning current, unit: A ; The structural coefficient is set to 0.

01. The width of the prefabricated cabin shielding mesh, in units of m ; The harmonic frequency of the lightning strike current, in units of . MHz .

7. The lightning protection design method for the grounding system of a prefabricated substation in a high-altitude mountainous area according to claim 5, characterized in that: Step 2.2 involves modeling the magnetic field inside LPZ2 within the prefabricated cabin. The specific formula is as follows: in, The shielding coefficient is calculated using the following formula: in: The grid width for the grid-type spatial shielding, in units of m ; The radius of the grid-type shielded conductor, in units of m ; Lightning strike density, measured in strikes per second. km ² / year.

8. The lightning protection design method for the grounding system of a prefabricated substation in a high-altitude mountainous area according to claim 2, characterized in that: Step 3 specifically includes the following steps: Step 3.1: The measurement area is divided into zones using the K-means clustering algorithm. Based on the soil resistivity data obtained in Step 1, a multi-layer soil model is established using the least squares method. Sum of squared errors function Defined as: in, It is the first The resistivity measured this time. It is the first The depth measured in this measurement These are model predictions. The parameter vector to be determined; right Regarding each parameter separately ( Find the partial derivatives and set them equal to 0 to obtain the system of equations: =0 Solving this equation yields the vector. Relationship with function ; Using the coefficient of determination To evaluate the accuracy of the modeling, ; in, It is the average of the measured values; Step 3.2: Apply the obtained multi-layer soil model to the grounding system design, and calculate the grounding system performance indicators based on the soil model. The grounding system performance indicators include grounding resistance, contact voltage, step voltage, and grounding short-circuit current. Step 3.3: Dynamically adjust the length of the grounding conductor based on the regional lightning strike density. The length of the grounding conductor is: in, This is a correction factor for geological type; The average soil resistivity; This refers to the density of lightning strikes.

9. The lightning protection design method for the grounding system of a prefabricated substation in a high-altitude mountainous area according to claim 8, characterized in that: Step 3.2 involves calculating the performance indicators of the grounding system, including: Calculate the grounding resistance of the horizontal grounding grid and grounding resistance of deep well grounding electrode The calculation formula is: Where, constant ;constant ; The area of ​​the horizontal grounding grid is expressed in units of... ; The diameter or equivalent diameter of the horizontal grounding electrode, in units of m ; The burial depth of the horizontal grounding electrode, in units of m ; The total length of the outer edge of the grounding grid, in units of m ; The total length of the horizontal grounding electrode, in units of m ; Soil resistivity, unit: ; Calculate contact voltage Step voltage and target grounding resistance The calculation formula is: in, The total time for the short-circuit current to flow, in units of s ; The resistivity of the ground soil at the position where a person is standing; The soil attenuation coefficient; Frequency-related factors; The formula for calculating the short-circuit current to ground after a lightning strike is as follows: in, This refers to the maximum short-circuit fault current of the substation as specified in the design specifications. This is the diversion coefficient; This is the attenuation coefficient.

10. The lightning protection design method for the grounding system of a prefabricated substation in a high-altitude mountainous area according to any one of claims 1-9, characterized in that: Step 4 specifically includes the following steps: Step 4.1: Evaluate the lightning protection effect and obtain a safety score; Step 4.2: Environmental performance evaluation, obtaining an environmental performance score; Step 4.3: Based on the evaluation results from various dimensions, the prefabricated cabin lightning protection green safety design index is obtained. Environmental rating+ Safety rating; in, As a weighting factor in the environmental rating, The weights for the security score, and .

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