Transmission line lightning strike risk assessment system, method and storage medium

Abstract

This invention discloses a system, method, and storage medium for assessing the lightning strike risk of transmission lines. The method includes: dividing the mountain and surrounding flat area into several extraction sections; defining the boundary of mesoscopic terrain based on the lightning density variation coefficient of the extraction sections and the average lightning density variation coefficient of the flat area; defining the range from the boundary of the mesoscopic terrain to the mountain peak as mesoscopic-scale terrain; establishing a mesoscopic-scale lightning downlink leader fractal development model based on the spatial electric field of the mesoscopic-scale terrain, and simulating the model to obtain the ground lightning distribution of the mesoscopic terrain; using the ground lightning distribution of the mesoscopic terrain as the lightning density of each region of the complex terrain; calculating the transmission line lightning trip rate of each region of the complex terrain based on the lightning density and lightning observation data; and assessing the lightning strike risk of each region of the complex terrain based on the transmission line lightning trip rate. This invention provides a more refined method for assessing the lightning strike risk of transmission lines in complex terrain areas.

Description

Technical Field

[0001] This invention relates to the field of lightning strike risk assessment technology for power transmission lines, specifically to a lightning strike risk assessment system and method for power transmission lines and a storage medium thereon, and more particularly to a lightning strike risk assessment system and method for power transmission lines that incorporates mesoscale topography and a storage medium thereon. Background Technology

[0002] Lightning has become a serious threat to the safe operation of transmission lines, making lightning strike risk assessment a crucial task in power system operation and maintenance. Current traditional lightning strike risk assessment methods primarily rely on statistical data on regional thunderstorm activity under macroscopic topography. However, this method is not ideal for areas with complex terrain, as transmission lines traverse large areas with varied topography, and even within the same region, different terrain features can significantly impact the lightning strike risk assessment results. Existing technologies have not fully resolved the problem of accurately assessing lightning strike risk for transmission lines in complex terrain areas. Therefore, a new method is needed to more accurately assess the lightning strike risk of transmission lines in such regions.

[0003] Existing technology discloses "a risk assessment method for transmission lines," which comprehensively considers equipment risk values ​​based on condition assessment, transmission line overload risk values, and static voltage exceedance risk values, assigns corresponding dynamic weight values ​​to each risk value, and calculates the comprehensive risk value of the transmission line. However, this method lacks a corresponding assessment method for lightning strike risk, and therefore cannot meet the overall risk assessment needs of transmission lines.

[0004] Existing technology discloses "a method and related equipment for assessing the lightning risk of transmission lines." This method proposes to plot the lightning density of a buffer zone based on lightning data, simultaneously compare historical tripping data and historical lightning density, and then classify the lightning risk according to the lightning distance, lightning density, historical lightning density, and real-time meteorological data to obtain the lightning risk of transmission lines. However, the method still cannot assess the lightning risk in areas with complex terrain. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies in assessing lightning risk in complex terrain areas. Therefore, further processing of macroscopic terrain is needed, and this invention proposes a lightning risk assessment method that integrates mesoscopic terrain data. This allows for a more refined assessment of lightning risk for transmission lines in complex terrain areas, resulting in a lightning risk assessment system, method, and storage medium for transmission lines. The system first divides the complex terrain area into mesoscopic scale sections and establishes a lightning downlink leader fractal development model based on these sections. Then, it simulates the downlink leader fractal development model to obtain the ground flash density in each region of the mesoscopic terrain. Finally, it calculates the lightning tripping rate of transmission lines in complex terrain areas using the ground flash density in each region of the mesoscopic terrain and lightning observation data, thereby assessing the lightning risk. This invention proposes a ground lightning distribution model based on mesoscopic terrain, which lies between macroscopic and microscopic terrain, thus enabling a more refined assessment of lightning risk for transmission lines in complex terrain areas and providing technical support for lightning risk assessment of transmission lines in complex terrain.

[0006] To achieve this objective, the first aspect of the present invention proposes a transmission line lightning strike risk assessment system, comprising: a terrain scale division module, used to divide the mountain and the flat area outside the mountain's critical area into several extraction segments, to divide the boundary of the mesoscopic terrain according to the lightning density variation coefficient of the extraction segments and the average lightning density variation coefficient of the flat area, and to divide the range from the boundary of the mesoscopic terrain to the mountain's apex into mesoscopic scale terrain.

[0007] The ground lightning distribution module is used to establish a mesoscopic terrain lightning downlink leader fractal development model based on the spatial electric field of the mesoscopic terrain. By simulating the mesoscopic terrain lightning downlink leader fractal development model, the ground lightning distribution of the mesoscopic terrain is obtained.

[0008] The lightning risk assessment module is used to take the ground lightning distribution of the mesoscopic terrain as the ground flash density of each area of ​​the terrain to be assessed, calculate the lightning trip rate of the transmission lines in each area of ​​the terrain to be assessed based on the ground flash density and lightning observation data, and assess the lightning risk of each area of ​​the terrain to be assessed through the lightning trip rate of the transmission lines.

[0009] Furthermore, the specific method for dividing the mountain and the flat area outside the mountain's critical zone into several extraction segments is as follows: the three-dimensional space formed by the width of the mountain, the height of the mountain, and the flat area outside the mountain's critical zone is used as the research space for mesoscopic topographic scale division, and the research space is divided into several extraction segments with the same distance along the extraction direction from the flat area to the mountain area.

[0010] Furthermore, the specific method for delineating the boundary of mesoscopic topography based on the coefficient of variation of lightning density in the extracted section and the average coefficient of variation of lightning density in the flat area is as follows: calculate the coefficient of variation of lightning density in several extracted sections respectively, and compare the obtained coefficients of variation of lightning density in several extracted sections with the average coefficient of variation of lightning density in the flat area within the study space. If the coefficient of variation of lightning density in the extracted section is greater than the coefficient of variation of lightning density in the flat area, then the extracted section is the critical section of the mesoscopic topography scale within the study space, and the midpoint of the critical section is taken as the boundary of the mesoscopic topography.

[0011] Furthermore, the specific method for establishing a mesoscale terrain lightning downlink leader fractal development model based on the spatial electric field of the mesoscale terrain is as follows: the mesoscale terrain is divided into a grid of discrete grid points with equal spacing, and the potential relationship of the spatial electric field formed by each discrete grid point within the grid is shown in the following equation:

[0012]

[0013] In the formula, Let $\frac{i}{j}$ be the potential of the grid point in the $i$-th row and $j$-th column. Let $\frac{i+1}{j}$ be the potential of the grid point in the (i+1)th row and the (j)th column. Let $\frac{i}{j+1}$ be the potential of the grid point in the $i$-th row and $j+1$-th column. Let $\frac{i}{j-1}$ be the potential of the grid point in the $i$-th row and $j-1$-th column. Let be the potential of the grid point in the (i-1)th row and jth column of the grid;

[0014] Equation (1) is calculated using the over-relaxation iteration method, and the potential relationship of the spatial electric field of the mesh after iteration is shown in the following equation:

[0015]

[0016] In the formula, After the nth iteration The value of ω, where ω is the relaxation factor. After the (n+1)th iteration The value, After the (n+1)th iteration The value, After the (n+1)th iteration The value, After the (n+1)th iteration The value, After the (n+1)th iteration The value;

[0017] The formula for calculating the optimal relaxation factor that makes the iterative process converge fastest in equation (2) is as follows:

[0018]

[0019] In the formula, ω0 is the optimal relaxation factor, and n and m are the number of grids divided on both the length and width sides of the mesoscopic-scale terrain within the rectangular region, respectively.

[0020] The potential development point of the downlink lightning leader is determined based on the discharge grid points inside the lightning discharge channel in the mesoscale topography, and the determination formula is as follows:

[0021]

[0022] In the formula, E is the average field strength between the discharge grid points inside the lightning discharge channel and the potential development point of the lightning downward leader. Let E be the potential difference between the discharge grid points inside the lightning discharge channel and the potential development point of the downward lightning leader, and let L be the actual distance between the discharge grid points inside the lightning discharge channel and the potential development point of the downward lightning leader. c E is the critical discharge field strength. c =216kV / m;

[0023] The probability of a potential development point for a downlink lightning leader is shown in the following formula:

[0024]

[0025] In the formula, The development of discharge grid point N within the lightning discharge channel into potential development point N of the downlink lightning leader. * The probability, From the discharge grid point N inside the lightning discharge channel to the potential development point N of the downlink lightning leader. * The electric field strength between them, where η is the development probability exponent, E c E is the critical discharge field strength. c =216kV / m;

[0026] If a potential development point of a downlink lightning leader develops into a discharge grid point within a new lightning discharge channel, the potential calculation formula for the potential development point of the downlink lightning leader is as follows:

[0027]

[0028] In the formula, To develop into a potential development point N for a new lightning downlink leader within a lightning discharge channel. * The potential, E represents the potential of discharge grid point N within the lightning discharge channel. ch The electric field strength inside the new lightning discharge channel. From discharge grid point N to potential development point N * The distance between them.

[0029] Furthermore, the specific method for simulating the mesoscopic terrain lightning downlink leader fractal development model to obtain the mesoscopic terrain ground lightning distribution is as follows: calculate the potential and electric field intensity of each grid point in the mesoscopic terrain, and continuously calculate the position and potential of the potential development point of the lightning downlink leader through the mesoscopic terrain lightning downlink leader fractal development model. When the potential development point of the lightning downlink leader undergoes a jump, the simulation of one lightning strike process is completed. Repeat the above process until the simulation of t lightning strike processes is completed, and record the coordinates of all lightning strike points to obtain the mesoscopic terrain ground lightning distribution.

[0030] Furthermore, the specific method for calculating the transmission line lightning trip rate in each area of ​​the terrain to be assessed based on the flashover density and lightning observation data is as follows: The calculation formula for the backflashover trip rate, obtained from the flashover density and lightning observation data in each area of ​​the terrain to be assessed, is as follows:

[0031] P f =N×g×P I ×η (7)

[0032]

[0033] In the formula, P f To represent the tripping rate, N is the total number of lightning strikes per year in the mesoscale terrain, g is the strike rate (1 / 6 for plains, 1 / 4 for mountains), and P... I η is the probability of a lightning current greater than I, η is the arc establishment rate, η = 0.4, Ng is the ground flash density in each area of ​​the terrain to be evaluated, b is the distance between the two lightning protection wires, and h is the height of the lightning protection wire above the ground.

[0034] The calculation formula for the bypass tripping rate, based on the ground flash density and lightning observation data of each terrain region to be evaluated, is as follows:

[0035]

[0036] f(I)=I max (0.1r max ) 1.54 (10)

[0037] In the formula, P r Let N be the tripping rate due to the circuit breaker, η be the arc-building rate (η = 0.4), ΔL be the collector line segment of length ΔL, and N be the tripping rate due to the circuit breaker. g To assess the ground flash density in different terrain regions, I max I is the maximum current amplitude at which a flashover occurs. C For the amplitude of the lightning current, l BDis the lightning exposure width, f(I) is the lightning current probability density function, and r max is the maximum shielding failure striking distance;

[0038] According to the cloud-to-ground flash density and lightning observation data of each region of the terrain to be evaluated, the calculation formula for the induced lightning trip rate is as follows:

[0039]

[0040] y max = 25H C I / U 50％ (12)

[0041]

[0042]

[0043] In the formula, P g is the induced lightning trip rate, D k is the distance from the direct strike point to the line, r c is the conductor striking distance, r g is the ground striking distance, H C is the distance from the tower conductor suspension point to the ground, y max is the flashover range of induced lightning, I is the induced lightning current, U 50％ is the 50% impulse flashover voltage of the insulator string, Ng is the cloud-to-ground flash density of each region of the terrain to be evaluated, η is the arc initiation rate, η = 0.4, I C is the lightning current amplitude, P(I) is the probability distribution function of the lightning current amplitude;

[0044] According to the backflash trip, shielding failure trip rate and induced lightning trip rate, the calculation formula for the lightning trip rate of the transmission line in each region of the terrain to be evaluated is as follows:

[0045]

[0046] In the formula, S is the average value of the lightning trip rates of each tower of the transmission line in each region of the terrain to be evaluated, T is the total number of towers of the entire transmission line, m is the theoretically calculated lightning trip rate of the tower, m is the sum of the backflash trip, shielding failure trip rate and induced lightning trip rate, and n is the number of tower bases.

[0047] Further, the specific method for evaluating the lightning risk of each region of the terrain to be evaluated through the lightning trip rate of the transmission line is as follows:

[0048] When m < 0.5S, it is considered that the lightning risk level of the towers in each region of the terrain to be evaluated is Class I;

[0049] When 0.5S < m < S, it is considered that the lightning risk level of the towers in each region of the terrain to be evaluated is Class II;

[0050] When S < m < 1.5S, it is considered that the lightning strike risk level of the transmission towers in each area of the terrain to be evaluated is level III;

[0051] When m > 1.5S, it is considered that the lightning strike risk level of the transmission towers in each area of the terrain to be evaluated is level IV.

[0052] The second aspect of the present invention proposes a method for evaluating the lightning strike risk of a transmission line, including:

[0053] Dividing the mountain body and the flat area outside the critical area of the mountain body into several extraction sections, dividing the boundary of the mesoscopic terrain according to the coefficient of variation of the ground flash density of the extraction sections, and dividing the range from the boundary of the mesoscopic terrain to the vertex of the mountain body into mesoscopic-scale terrain;

[0054] Establishing a mesoscopic terrain lightning downward leader fractal development model according to the spatial electric field of the mesoscopic-scale terrain, and obtaining the ground lightning strike distribution of the mesoscopic terrain through simulation calculation of the mesoscopic terrain lightning downward leader fractal development model;

[0055] Taking the ground lightning strike distribution of the mesoscopic terrain as the ground flash density of each area of the terrain to be evaluated, calculating the lightning trip rate of the transmission line in each area of the terrain to be evaluated according to the ground flash density and lightning observation data of each area of the terrain to be evaluated, and evaluating the lightning strike risk of each area of the terrain to be evaluated through the lightning trip rate of the transmission line.

[0056] Further, the specific method for dividing the mountain body and the flat area outside the critical area of the mountain body into several extraction sections is: taking the three-dimensional space formed by the width of the mountain body, the height of the mountain body, and the flat area outside the critical area of the mountain body as the research space for mesoscopic terrain scale division, and dividing the research space into several extraction sections with the same distance in the extraction direction from the flat area to the mountain area along the extraction direction.

[0057] Further, the specific method for dividing the boundary of the mesoscopic terrain according to the coefficient of variation of the ground flash density of the extraction sections and the average coefficient of variation of the ground flash density of the flat area is: calculating the coefficient of variation of the ground flash density of several extraction sections respectively, and comparing the obtained coefficients of variation of the ground flash density of several extraction sections with the average coefficient of variation of the ground flash density of the flat area in the research space. If the coefficient of variation of the ground flash density of the extraction section is greater than the coefficient of variation of the ground flash density of the flat area, then the extraction section is the critical section of the mesoscopic terrain scale in the research space, and taking the midpoint of the critical section as the boundary of the mesoscopic terrain.

[0058] Furthermore, the specific method for establishing a mesoscale terrain lightning downlink leader fractal development model based on the spatial electric field of the mesoscale terrain is as follows: the mesoscale terrain is divided into a grid of discrete grid points with equal spacing, and the potential relationship of the spatial electric field formed by each discrete grid point within the grid is shown in the following equation:

[0059]

[0060] In the formula, Let $\frac{i}{j}$ be the potential of the grid point in the $i$-th row and $j$-th column. Let $\frac{i+1}{j}$ be the potential of the grid point in the (i+1)th row and the (j)th column. Let $\frac{i}{j+1}$ be the potential of the grid point in the $i$-th row and $j+1$-th column. Let $\frac{i}{j-1}$ be the potential of the grid point in the $i$-th row and $j-1$-th column. Let be the potential of the grid point in the (i-1)th row and jth column of the grid;

[0061] Equation (1) is calculated using the over-relaxation iteration method, and the potential relationship of the spatial electric field of the mesh after iteration is shown in the following equation:

[0062]

[0063] In the formula, After the nth iteration The value of ω, where ω is the relaxation factor. After the (n+1)th iteration The value, After the (n+1)th iteration The value, After the (n+1)th iteration The value, After the (n+1)th iteration The value, After the (n+1)th iteration The value;

[0064] The formula for calculating the optimal relaxation factor that makes the iterative process converge fastest in equation (2) is as follows:

[0065]

[0066] In the formula, ω0 is the optimal relaxation factor, and n and m are the number of grids divided on both the length and width sides of the mesoscopic-scale terrain within the rectangular region, respectively.

[0067] The potential development point of the downlink lightning leader is determined based on the discharge grid points inside the lightning discharge channel in the mesoscale topography, and the determination formula is as follows:

[0068]

[0069] In the formula, E is the average field strength between the discharge grid points inside the lightning discharge channel and the potential development point of the lightning downward leader. Let E be the potential difference between the discharge grid points inside the lightning discharge channel and the potential development point of the downward lightning leader, and let L be the actual distance between the discharge grid points inside the lightning discharge channel and the potential development point of the downward lightning leader. c E is the critical discharge field strength. c =216kV / m;

[0070] The probability of a potential development point for a downlink lightning leader is shown in the following formula:

[0071]

[0072] In the formula, The development of discharge grid point N within the lightning discharge channel into potential development point N of the downlink lightning leader. * The probability, From the discharge grid point N inside the lightning discharge channel to the potential development point N of the downlink lightning leader. * The electric field strength between them, where η is the development probability exponent, E c E is the critical discharge field strength. c =216kV / m;

[0073] If a potential development point of a downlink lightning leader develops into a discharge grid point within a new lightning discharge channel, the potential calculation formula for the potential development point of the downlink lightning leader is as follows:

[0074]

[0075] In the formula, The potential of N*, which is the potential development point for a downward lightning leader within a new lightning discharge channel, E represents the potential of discharge grid point N within the lightning discharge channel. ch The electric field strength inside the new lightning discharge channel. From discharge grid point N to potential development point N * The distance between them.

[0076] Furthermore, the specific method for calculating the transmission line lightning trip rate in each area of ​​the terrain to be assessed based on the flashover density and lightning observation data is as follows: The calculation formula for the backflashover trip rate, obtained from the flashover density and lightning observation data in each area of ​​the terrain to be assessed, is as follows:

[0077] P f =N×g×P I ×η (7)

[0078]

[0079] In the formula, P f To represent the tripping rate, N is the total number of lightning strikes per year in the mesoscale terrain, g is the strike rate (1 / 6 for plains, 1 / 4 for mountains), and P... I Let I be the probability of a lightning current greater than I, and η be the arc-building rate, η = 0.4, N g The lightning density in each area of ​​the terrain to be evaluated is given by b, the distance between the two lightning rods is given by h, and the height of the lightning rod above the ground is given by h.

[0080] The calculation formula for the bypass tripping rate, based on the ground flash density and lightning observation data of each terrain region to be evaluated, is as follows:

[0081]

[0082] f(I)=I max (0.1r max ) 1.54 (10)

[0083] In the formula, P r Let N be the tripping rate due to the circuit breaker, η be the arc-building rate (η = 0.4), ΔL be the collector line segment of length ΔL, and N be the tripping rate due to the circuit breaker. g To assess the ground flash density in different terrain regions, I max I is the maximum current amplitude at which a flashover occurs. C For the amplitude of the lightning current, l BD Let f(I) be the lightning exposure width, f(I) be the lightning current probability density function, and r be the lightning current probability density function. max This is the maximum circumduction distance;

[0084] The formula for calculating the induced lightning tripping rate, based on the ground flash density and lightning observation data of each area of ​​the terrain to be evaluated, is as follows:

[0085]

[0086] y max =25H c I / U 50％ (12)

[0087]

[0088]

[0089] In the formula, P g D is the tripping rate due to induced lightning. k r is the distance from the point of impact to the line. c For conductor striking distance, r g H is the ground impact distance. C y is the distance from the suspension point of the conductor on the tower to the ground. maxis the flashover range of induced lightning, I is the induced lightning current, U 50％ the 50% impulse flashover voltage of the insulator string, N g is the ground flash density of each area of the terrain to be evaluated, η is the arc building rate, η = 0.4, I C is the lightning current amplitude, P(I) is the probability function of the lightning current amplitude distribution;

[0090] According to the back-strike tripping rate, shielding failure tripping rate and induced lightning tripping rate, the calculation formula for the lightning tripping rate of the transmission line in each area of the terrain to be evaluated is as follows:

[0091]

[0092] In the formula, S is the average value of the lightning tripping rate of each tower of the transmission line in each area of the terrain to be evaluated, T is the total number of towers of the entire transmission line, m is the theoretical calculated lightning tripping rate of the tower, m is the sum of the back-strike tripping rate, shielding failure tripping rate and induced lightning tripping rate, and n is the number of tower bases.

[0093] Furthermore, the specific method for evaluating the lightning risk of each area of the terrain to be evaluated through the lightning tripping rate of the transmission line is:

[0094] When m < 0.5S, it is considered that the lightning risk level of the towers in each area of the terrain to be evaluated is level I;

[0095] When 0.5S < m < S, it is considered that the lightning risk level of the towers in each area of the terrain to be evaluated is level II;

[0096] When S < m < 1.5S, it is considered that the lightning risk level of the towers in each area of the terrain to be evaluated is level III;

[0097] When m > 1.5S, it is considered that the lightning risk level of the towers in each area of the terrain to be evaluated is level IV.

[0098] The third aspect of the present invention proposes a computer-readable storage medium, the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the above method are implemented.

[0099] The beneficial effects of the present invention:

[0100] Traditional methods for assessing lightning risk of transmission lines only consider the macroscopic lightning distribution on the ground, neglecting internal topographic variations or the influence of microscopic topography on lightning bypass rates while ignoring the impact of microscopic topography on ground lightning distribution. Therefore, this invention first divides complex terrain areas into mesoscopic scales and establishes a lightning downlink leader fractal development model based on these mesoscopic scales. Then, it simulates the downlink leader fractal development model to obtain the ground flash density in each region of the mesoscopic topography. Finally, it calculates the lightning tripping rate of transmission lines in complex terrain areas using the ground flash density in each region of the mesoscopic topography and lightning observation data, thereby assessing the lightning risk. This invention, based on the ground lightning distribution of mesoscopic topography (between macroscopic and microscopic topography), integrates a method for assessing lightning risk of transmission lines in complex terrain areas, providing technical support for lightning risk assessment of transmission lines in complex terrain. This method is used to assess the lightning risk of transmission lines in complex terrain areas, classify lightning risk levels, and assist in the construction of lightning protection systems for transmission lines in complex terrain areas. Attached Figure Description

[0101] Figure 1 This is a structural block diagram of a power transmission line lightning strike risk assessment system according to the present invention;

[0102] Figure 2 This is a schematic diagram illustrating the intermediate topographic scale division of the present invention;

[0103] Figure 3 This is a schematic diagram of the intermediate topographic lightning downlink leader fractal development model of the present invention;

[0104] Figure 4 This is a flowchart illustrating the simulation of lightning strike distribution patterns on the ground in the intermediate terrain of this invention.

[0105] Figure 5 This is a schematic diagram of the lightning tripping rate of each tower of the transmission line in complex terrain areas in this invention. Detailed Implementation

[0106] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0107] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0108] Example 1

[0109] The first aspect of this invention proposes a lightning strike risk assessment system for power transmission lines, such as... Figure 1 As shown, it includes a terrain scale division module, a ground lightning strike distribution module, and a lightning strike risk assessment module;

[0110] The topographic scale division module is used to divide the mountain and the flat area outside the mountain's critical area into several extraction segments. Based on the coefficient of variation of the ground flash density of the extraction segments and the average coefficient of variation of the ground flash density of the flat area, the boundary of the mesoscopic topography is divided, and the range from the boundary of the mesoscopic topography to the top of the mountain is divided into mesoscopic scale topography.

[0111] The ground lightning strike distribution module is used to establish a mesoscopic terrain lightning downlink leader fractal development model based on the spatial electric field of the mesoscopic terrain. By simulating the mesoscopic terrain lightning downlink leader fractal development model, the ground lightning strike distribution of the mesoscopic terrain is obtained.

[0112] The lightning risk assessment module uses the ground lightning distribution of the mesoscopic terrain as the ground flash density of each area of ​​the terrain to be assessed, calculates the lightning trip rate of the transmission lines in each area of ​​the terrain to be assessed based on the ground flash density and lightning observation data, and assesses the lightning risk of each area of ​​the terrain to be assessed through the lightning trip rate of the transmission lines.

[0113] In the above technical solution, the mountain transitions to the flat area through a critical zone.

[0114] In the above technical solution, the system also includes a data acquisition module, which mainly collects mesoscale topographic data and lightning strike observation data. The mesoscale topographic data includes the standard deviation σ of lightning density and the average value μ of lightning density in the extracted section and flat area. The lightning strike observation data includes lightning strike density and lightning current amplitude probability. The formula for calculating lightning strike density is as follows:

[0115]

[0116] In the formula, N L The number of lightning strikes per square kilometer per year; T d The average number of days with lightning per year, for T d In regions where N = 40, L =0.07, for T d =80, N L =0.086.

[0117] In the above technical solution, the calculation formula for the probability distribution of lightning current amplitude is shown below:

[0118]

[0119] In the above technical solution, the correction formula for an annual average of less than 20 lightning days is as follows:

[0120]

[0121] In the formula, I is the amplitude of the lightning current, kA; P L It represents the probability that the lightning current amplitude is greater than I, %.

[0122] In the above technical solution, the formula for calculating the coefficient of variation of ground flash density is as follows:

[0123]

[0124] In the formula, C v σ is the coefficient of variation of lightning density, μ is the standard deviation of lightning density, and μ is the average value of lightning density.

[0125] In the above technical solution, the specific method for dividing the mountain and the surrounding flat area into several extraction segments is as follows: The three-dimensional space formed by the width of the mountain, the height of the mountain, and the flat area surrounding the mountain is used as the research space for mesoscopic topographical scale division. This research space is then divided into several extraction segments with the same distance along the extraction direction from the flat area to the mountain area. For example, using the research space as a three-dimensional space, the area from the mountain to the surrounding flat area is the x-axis, the width of the mountain is the y-axis, and the height of the mountain is the z-axis. In this text, "same distance" refers to dividing the x-axis into segments of equal length, such as... Figure 2 The extraction segments are shown as segment 1, segment 2, and segment 3.

[0126] In the above technical solution, the specific method for delineating the boundary of mesoscopic topography based on the coefficient of variation of lightning density in the extracted section and the average coefficient of variation of lightning density in the flat area is as follows: The coefficients of variation of lightning density in several extracted sections are calculated respectively, and the obtained coefficients of variation of lightning density in several extracted sections are compared with the average coefficient of variation of lightning density in the flat area within the study space. If the coefficient of variation of lightning density in the extracted section is greater than the coefficient of variation of lightning density in the flat area, then the extracted section is a critical section at the mesoscopic topographic scale within the study space. Figure 2 As shown, the coefficient of variation of lightning density in the extracted section 3 is greater than the average coefficient of variation of lightning density in the flat area. Therefore, the extracted section 3 is regarded as the critical section at the mesoscopic topographic scale.

[0127] According to lightning location system data, the lightning density map presents a curve similar to contour lines on a topographic map. In flat areas, the distribution of lightning strikes is uniform, meaning that the lightning density in flat areas fluctuates within a small range around the mean. However, the lightning density in mountainous areas is significantly higher than in flat areas. But mountains have a shielding effect on flat areas within a certain range around them, which causes the lightning density in some flat areas near the foot of the mountain to be significantly lower than in other flat areas. Therefore, the critical zone only appears in flat areas near the foot of the mountain, while the lightning density in flat areas further away fluctuates within a small range around the mean.

[0128] In the above technical solution, the midpoint of the critical segment is used as the boundary of the mesoscopic terrain. However, considering the randomness of the data, the midpoint of extraction segment 3 and extraction segment 2 are used as the boundary for dividing the mesoscopic terrain. Figure 2 As shown, the right-side scale range of the mesotope is the distance from the midpoint of extracted segment 2 to the mountaintop; the left-side scale range of the mesotope can be divided using the same method, and the superposition of the left and right sides is the scale range of the entire mesotope. Considering that there are cases in actual terrain where there is only a flat area on one side, when dividing the scale in this special case, the scale of the side with the flat area is used as the scale range of the mesotope.

[0129] In this invention, the height and slope of the mountain have a significant impact on the mesoscopic topographic scale division results. Since the mountain has an attractive effect on lightning, it will have a shielding effect on the foot of the mountain, resulting in a decrease in lightning density and thus an increase in the lightning density variation coefficient. Therefore, the higher the mountain and the greater the slope, the greater the attraction of the mountain to lightning. At the same time, the shielding range on the foot of the mountain expands, and the points where the lightning density variation coefficient increases are further away from the mountain. Ultimately, the distance between the mesoscopic topographic critical section and the mountain is greater, and the influence of the topography on the distribution of ground lightning strikes is more obvious.

[0130] In the above technical solution, the specific method for establishing a mesoscale topographic lightning downlink leader fractal development model based on the spatial electric field of the mesoscale topography is as follows: the mountain model is replaced by an isosceles triangle. To facilitate the calculation of the spatial electric field, the space of the mesoscale topography is discretized into a series of equally spaced grid points. The entire space is divided into a 5m×5m square grid, with the mountain area further divided into a finer 1m×1m square grid. The endpoints of all grids are used to represent the entire study space, such as... Figure 3 As shown, the potential relationship of the spatial electric field formed by each discrete grid point within the grid is given by the following equation:

[0131]

[0132] In the formula, Let $\frac{i}{j}$ be the potential of the grid point in the $i$-th row and $j$-th column. Let $\frac{i+1}{j}$ be the potential of the grid point in the (i+1)th row and the (j)th column. Let $\frac{i}{j+1}$ be the potential of the grid point in the $i$-th row and $j+1$-th column. Let $\frac{i}{j-1}$ be the potential of the grid point in the $i$-th row and $j-1$-th column. Let be the potential of the grid point in the (i-1)th row and jth column of the grid.

[0133] In the above technical solution, the potential relationship of the spatial electric field formed by the grid points is calculated using the over-relaxation iteration method, and the potential relationship of the spatial electric field of the grid after iteration is shown in the following equation:

[0134]

[0135] In the formula, After the nth iteration The value of ω, where ω is the relaxation factor. After the (n+1)th iteration The value, After the (n+1)th iteration The value, After the (n+1)th iteration The value, After the (n+1)th iteration The value, After the (n+1)th iteration The value of is obtained by using the spatial electric field of the grid after over-relaxation iteration to provide the background field strength for subsequent calculation of the mesoscopic topographic lightning downlink leader fractal development model.

[0136] In the above technical solution, the formula for calculating the optimal relaxation factor that makes the iteration process converge fastest is as follows:

[0137]

[0138] In the formula, ω0 is the optimal relaxation factor, and n and m are the number of grids divided on the length and width sides of the mesoscopic terrain within the rectangular region, respectively. Generally, the more grid nodes there are, the larger the optimal relaxation factor becomes. When the relaxation factor used is less than the optimal value, the convergence process is monotonic, and the convergence speed increases with the increase of the relaxation factor.

[0139] In the above technical solution, the lightning downlink leader develops vertically from the upper boundary of the thundercloud towards the ground, such as... Figure 3As shown, the upper boundary of the thundercloud to the ground is simplified into a two-dimensional plane, divided into a lattice map. Each step of the downlink leader's development process can be simplified as development from the grid points inside the lightning discharge channel to the undischarged grid points within a specified step range around the lightning discharge channel. If the average field strength between the undischarged grid points and a point in the lightning discharge channel meets certain conditions, then that point is a potential development point of the downlink leader. Therefore, the potential development point of the downlink leader is determined based on the discharge grid points inside the lightning discharge channel in the mesoscale topography, and the determination formula is as follows:

[0140]

[0141] In the formula, E is the average field strength between the discharge grid points inside the lightning discharge channel and the potential development point of the lightning downward leader. Let E be the potential difference between the discharge grid points inside the lightning discharge channel and the potential development point of the downward lightning leader, and let L be the actual distance between the discharge grid points inside the lightning discharge channel and the potential development point of the downward lightning leader. c E is the critical discharge field strength. c =216kV / m. In this paper, the lightning discharge channel is... Figure 3 The line segments connecting the solid black dots represent the discharge grid points. Figure 3 The black solid dots in the middle Figure 3 The white dots in the diagram represent undischarged grid points. Figure 3 When the average field strength between the white dot in the diagram and the discharge grid points inside the lightning discharge channel satisfies the judgment formula for potential development points of a downlink lightning leader, the white dot can be determined as a potential development point of a downlink lightning leader.

[0142] In the above technical solution, the probability of the development of a potential lightning downlink leader development point is shown in the following formula:

[0143]

[0144] In the formula, The development of discharge grid point N within the lightning discharge channel into potential development point N of the downlink lightning leader. * The probability, From the discharge grid point N inside the lightning discharge channel to the potential development point N of the downlink lightning leader. * The electric field strength between them, where η is the development probability exponent, and η takes a value of 1, E c E is the critical discharge field strength. c =216kV / m.

[0145] In the above technical solution, if the potential development point of the downlink lightning leader develops into a discharge grid point inside a new lightning discharge channel, then the potential calculation formula for the potential development point of the downlink lightning leader is as follows:

[0146]

[0147] In the formula, To develop into a potential development point N for a new lightning downlink leader within a lightning discharge channel. * The potential, E represents the potential of discharge grid point N within the lightning discharge channel. ch The electric field strength inside the new lightning discharge channel. From discharge grid point N to potential development point N * The distance between them.

[0148] In the above technical solution, the specific method for simulating the mesoscopic topographic lightning downlink leader fractal development model to obtain the mesoscopic topographic ground lightning distribution is as follows: The development of the lightning downlink leader fractal is simulated using COMSOL simulation software, such as... Figure 4 As shown, first, the cloud potential, leader initiation position, and development step size are input. Then, the mountain height, mountain width, and other mountain modeling parameters are input. The potential and electric field intensity of each grid point in the mesoscale terrain are calculated. The position and potential of the potential development point of the lightning downlink leader are continuously calculated through the mesoscale terrain lightning downlink leader fractal development model. When the potential development point of the lightning downlink leader undergoes a jump, the simulation of one lightning strike process is completed. The above process is repeated until the simulation of t lightning strike processes is completed, and the coordinates of all lightning strike points are recorded to obtain the ground lightning distribution of the mesoscale terrain. In this paper, the judgment of the potential development point jump of the lightning downlink leader is as follows: when the average field strength between the uplink and downlink leaders or between the downlink leader and a target object that has not generated an uplink leader (an uplink leader refers to a phenomenon caused by a strong electric field on a target object, and the criterion is used to determine whether the target object generates an uplink leader) exceeds the average critical field strength of 500 kV / m, or when the uplink and downlink leaders meet, the final jump of the lightning strike occurs; the thundercloud potential is set to -200 MV; and the development step size is set to 20 m.

[0149] In the above technical solution, the specific method for calculating the lightning trip rate of transmission lines in complex terrain areas based on the ground flash density and lightning observation data of each area to be evaluated is as follows: The calculation formula for the backflashover trip rate based on the ground flash density and lightning observation data of each area to be evaluated is as follows:

[0150] P f =N×g×P I ×η

[0151]

[0152] In the formula, P fTo represent the tripping rate, N is the total number of lightning strikes per year in the mesoscale terrain, g is the strike rate (1 / 6 for plains, 1 / 4 for mountains), and P... I Let I be the probability of a lightning current greater than I, and η be the arc-building rate, η = 0.4, N g The lightning density in each area of ​​the terrain to be evaluated is given by b, the distance between the two lightning rods is given by h, and the height of the lightning rod above the ground is given by h.

[0153] In the above technical solution, the calculation formula for the bypass tripping rate, obtained based on the ground flash density and lightning observation data of each area of ​​the terrain to be evaluated, is as follows:

[0154]

[0155] f(I)=I max (0.1r max ) 1.54

[0156] In the formula, P r Let N be the tripping rate due to the circuit breaker, η be the arc-building rate (η = 0.4), ΔL be the collector line segment of length ΔL, and N be the tripping rate due to the circuit breaker. g To assess the ground flash density in different terrain regions, I max I is the maximum current amplitude at which a flashover occurs. C For the amplitude of the lightning current, l BD Let f(I) be the lightning exposure width, f(I) be the lightning current probability density function, and r be the lightning current probability density function. max This represents the maximum distance for a circumferential strike.

[0157] In the above technical solution, the calculation formula for the induced lightning tripping rate, based on the ground flash density and lightning observation data of each area of ​​the terrain to be evaluated, is as follows:

[0158]

[0159] y max =25H C I / U 50％

[0160]

[0161]

[0162] In the formula, P g D is the tripping rate due to induced lightning. k r is the distance from the point of impact to the line. c For conductor striking distance, r g H is the ground impact distance. C y is the distance from the suspension point of the conductor on the tower to the ground. max U represents the flashover range of induced lightning, I represents the induced lightning current, and U represents the flashover range of induced lightning. 50％50% impulse flashover voltage of insulator string, N g is the ground flash density of each area of the terrain to be evaluated, η is the arc initiation rate, η = 0.4, I C is the amplitude of lightning current, and P(I) is the probability distribution function of lightning current amplitude.

[0163] In the above technical solution, the calculation formula for the lightning trip rate of the transmission line in each area of the terrain to be evaluated obtained from the back-strike trip, shielding failure trip rate, and induced lightning trip rate is as follows:

[0164]

[0165] In the formula, S is the average value of the lightning trip rate of each tower of the transmission line in each area of the terrain to be evaluated, T is the total number of towers of the entire transmission line, m is the theoretically calculated lightning trip rate of the tower, m is the sum of the back-strike trip, shielding failure trip rate, and induced lightning trip rate, and n is the number of tower bases.

[0166] In the above technical solution, the specific method for evaluating the lightning strike risk of each area of complex terrain through the lightning trip rate of the transmission line is as follows: when m < 0.5S, it is considered that the lightning strike risk level of the towers in each area of complex terrain is level I, and level I is a low risk; when 0.5S < m < S, it is considered that the lightning strike risk level of the towers in each area of complex terrain is level II, and level II is a medium risk; when S < m < 1.5S, it is considered that the lightning strike risk level of the towers in each area of complex terrain is level III, and level III is a high risk; when m > 1.5S, it is considered that the lightning strike risk level of the towers in each area of complex terrain is level IV, and level IV is an extremely high risk.

[0167] Embodiment 2

[0168] The second aspect of the present invention proposes a method for evaluating the lightning strike risk of a transmission line, including:

[0169] Dividing the mountain body and the flat areas around the mountain body into several extraction sections, dividing the boundary of the mesoscopic terrain according to the coefficient of variation of the ground flash density of the extraction sections, and dividing the range from the boundary of the mesoscopic terrain to the vertex of the mountain body into mesoscopic-scale terrain;

[0170] Establishing a mesoscopic terrain lightning downward leader fractal development model based on the spatial electric field of the mesoscopic-scale terrain, and obtaining the ground lightning strike distribution of the mesoscopic terrain through simulation calculation of the mesoscopic terrain lightning downward leader fractal development model;

[0171] Taking the ground lightning strike distribution of the mesoscopic terrain as the ground flash density of each area of complex terrain, calculating the lightning trip rate of the transmission line in each area of complex terrain according to the ground flash density and lightning observation data of each area of the terrain to be evaluated, and evaluating the lightning strike risk of each area of complex terrain through the lightning trip rate of the transmission line.

[0172] In the above technical solution, the mountain transitions to the flat area through a critical zone.

[0173] In the above technical solution, the system also includes a data acquisition module, which mainly collects mesoscale topographic data and lightning strike observation data. The mesoscale topographic data includes the standard deviation σ of lightning density and the average value μ of lightning density in the extracted section and flat area. The lightning strike observation data includes lightning strike density and lightning current amplitude probability. The formula for calculating lightning strike density is as follows:

[0174]

[0175] In the formula, N L The number of lightning strikes per square kilometer per year; T d The average number of days with lightning per year, for T d In regions where N = 40, L =0.07, for T d =80, N L =0.086.

[0176] In the above technical solution, the calculation formula for the probability distribution of lightning current amplitude is shown below:

[0177]

[0178] In the above technical solution, the correction formula for an annual average of less than 20 lightning days is as follows:

[0179]

[0180] In the formula, I is the amplitude of the lightning current, kA; P L It represents the probability that the lightning current amplitude is greater than I, %.

[0181] In the above technical solution, the formula for calculating the coefficient of variation of ground flash density is as follows:

[0182]

[0183] In the formula, C v σ is the coefficient of variation of lightning density, μ is the standard deviation of lightning density, and μ is the average value of lightning density.

[0184] In the above technical solution, the specific method for dividing the mountain and the surrounding flat area into several extraction segments is as follows: The three-dimensional space formed by the width of the mountain, the height of the mountain, and the flat area surrounding the mountain is used as the research space for mesoscopic topographical scale division. This research space is then divided into several extraction segments with the same distance along the extraction direction from the flat area to the mountain area. For example, using the research space as a three-dimensional space, the area from the mountain to the surrounding flat area is the x-axis, the width of the mountain is the y-axis, and the height of the mountain is the z-axis. In this text, "same distance" refers to dividing the x-axis into segments of equal length, such as... Figure 2 The extraction segments are shown as segment 1, segment 2, and segment 3.

[0185] In the above technical solution, the specific method for delineating the boundary of mesoscopic topography based on the coefficient of variation of lightning density in the extracted section and the average coefficient of variation of lightning density in the flat area is as follows: The coefficients of variation of lightning density in several extracted sections are calculated respectively, and the obtained coefficients of variation of lightning density in several extracted sections are compared with the average coefficient of variation of lightning density in the flat area within the study space. If the coefficient of variation of lightning density in the extracted section is greater than the coefficient of variation of lightning density in the flat area, then the extracted section is a critical section at the mesoscopic topographic scale within the study space. Figure 2 As shown, the coefficient of variation of lightning density in the extracted section 3 is greater than the average coefficient of variation of lightning density in the flat area. Therefore, the extracted section 3 is regarded as the critical section at the mesoscopic topographic scale.

[0186] According to lightning location system data, the lightning density map presents a curve similar to contour lines on a topographic map. In flat areas, the distribution of lightning strikes is uniform, meaning that the lightning density in flat areas fluctuates within a small range around the mean. However, the lightning density in mountainous areas is significantly higher than in flat areas. But mountains have a shielding effect on flat areas within a certain range around them, which causes the lightning density in some flat areas near the foot of the mountain to be significantly lower than in other flat areas. Therefore, the critical zone only appears in flat areas near the foot of the mountain, while the lightning density in flat areas further away fluctuates within a small range around the mean.

[0187] In the above technical solution, the midpoint of the critical segment is used as the boundary of the mesoscopic terrain. However, considering the randomness of the data, the midpoint of extraction segment 3 and extraction segment 2 are used as the boundary for dividing the mesoscopic terrain. Figure 2As shown, the right-side scale range of the mesotope is the distance from the midpoint of extracted segment 2 to the mountaintop; the left-side scale range of the mesotope can be divided using the same method, and the superposition of the left and right sides is the scale range of the entire mesotope. Considering that there are cases in actual terrain where there is only a flat area on one side, when dividing the scale in this special case, the scale of the side with the flat area is used as the scale range of the mesotope.

[0188] In this invention, the height and slope of the mountain have a significant impact on the mesoscopic topographic scale division results. Since the mountain has an attractive effect on lightning, it will have a shielding effect on the foot of the mountain, resulting in a decrease in lightning density and thus an increase in the lightning density variation coefficient. Therefore, the higher the mountain and the greater the slope, the greater the attraction of the mountain to lightning. At the same time, the shielding range on the foot of the mountain expands, and the points where the lightning density variation coefficient increases are further away from the mountain. Ultimately, the distance between the mesoscopic topographic critical section and the mountain is greater, and the influence of the topography on the distribution of ground lightning strikes is more obvious.

[0189] In the above technical solution, the specific method for establishing a mesoscale topographic lightning downlink leader fractal development model based on the spatial electric field of the mesoscale topography is as follows: the mountain model is replaced by an isosceles triangle. To facilitate the calculation of the spatial electric field, the space of the mesoscale topography is discretized into a series of equally spaced grid points. The entire space is divided into a 5m×5m square grid, with the mountain area further divided into a finer 1m×1m square grid. The endpoints of all grids are used to represent the entire study space, such as... Figure 3 As shown, the potential relationship of the spatial electric field formed by each discrete grid point within the grid is given by the following equation:

[0190]

[0191] In the formula, Let $\frac{i}{j}$ be the potential of the grid point in the $i$-th row and $j$-th column. Let $\frac{i+1}{j}$ be the potential of the grid point in the (i+1)th row and the (j)th column. Let $\frac{i}{j+1}$ be the potential of the grid point in the $i$-th row and $j+1$-th column. Let $\frac{i}{j-1}$ be the potential of the grid point in the $i$-th row and $j-1$-th column. Let be the potential of the grid point in the (i-1)th row and jth column of the grid.

[0192] In the above technical solution, the potential relationship of the spatial electric field formed by the grid points is calculated using the over-relaxation iteration method, and the potential relationship of the spatial electric field of the grid after iteration is shown in the following equation:

[0193]

[0194] In the formula, After the nth iteration The value of ω, where ω is the relaxation factor. After the (n+1)th iteration The value, After the (n+1)th iteration The value, After the (n+1)th iteration The value, After the (n+1)th iteration The value, After the (n+1)th iteration The value of is obtained by using the spatial electric field of the grid after over-relaxation iteration to provide the background field strength for subsequent calculation of the mesoscopic topographic lightning downlink leader fractal development model.

[0195] In the above technical solution, the formula for calculating the optimal relaxation factor that makes the iteration process converge fastest is as follows:

[0196]

[0197] In the formula, ω0 is the optimal relaxation factor, and n and m are the number of grids divided on the length and width sides of the mesoscopic terrain within the rectangular region, respectively. Generally, the more grid nodes there are, the larger the optimal relaxation factor becomes. When the relaxation factor used is less than the optimal value, the convergence process is monotonic, and the convergence speed increases with the increase of the relaxation factor.

[0198] In the above technical solution, the lightning downlink leader develops vertically from the upper boundary of the thundercloud towards the ground, such as... Figure 3 As shown, the upper boundary of the thundercloud to the ground is simplified into a two-dimensional plane, divided into a lattice map. Each step of the downlink leader's development process can be simplified as development from the grid points inside the lightning discharge channel to the undischarged grid points within a specified step range around the lightning discharge channel. If the average field strength between the undischarged grid points and a point in the lightning discharge channel meets certain conditions, then that point is a potential development point of the downlink leader. Therefore, the potential development point of the downlink leader is determined based on the discharge grid points inside the lightning discharge channel in the mesoscale topography, and the determination formula is as follows:

[0199]

[0200] In the formula, E is the average field strength between the discharge grid points inside the lightning discharge channel and the potential development point of the lightning downward leader. Let E be the potential difference between the discharge grid points inside the lightning discharge channel and the potential development point of the downward lightning leader, and let L be the actual distance between the discharge grid points inside the lightning discharge channel and the potential development point of the downward lightning leader. c E is the critical discharge field strength. c =216kV / m. In this paper, the lightning discharge channel is... Figure 3The line segments connecting the solid black dots represent the discharge grid points. Figure 3 The black solid dots in the middle Figure 3 The white dots in the diagram represent undischarged grid points. Figure 3 When the average field strength between the white dot in the diagram and the discharge grid points inside the lightning discharge channel satisfies the judgment formula for potential development points of a downlink lightning leader, the white dot can be determined as a potential development point of a downlink lightning leader.

[0201] In the above technical solution, the probability of the development of a potential lightning downlink leader development point is shown in the following formula:

[0202]

[0203] In the formula, The development of discharge grid point N within the lightning discharge channel into potential development point N of the downlink lightning leader. * The probability, From the discharge grid point N inside the lightning discharge channel to the potential development point N of the downlink lightning leader. * The electric field strength between them, where η is the development probability exponent, and η takes a value of 1, E c E is the critical discharge field strength. c =216kV / m.

[0204] In the above technical solution, if the potential development point of the downlink lightning leader develops into a discharge grid point inside a new lightning discharge channel, then the potential calculation formula for the potential development point of the downlink lightning leader is as follows:

[0205]

[0206] In the formula, To develop into a potential development point N for a new lightning downlink leader within a lightning discharge channel. * The potential, E represents the potential of discharge grid point N within the lightning discharge channel. ch The electric field strength inside the new lightning discharge channel. From discharge grid point N to potential development point N * The distance between them.

[0207] In the above technical solution, the specific method for simulating the mesoscopic topographic lightning downlink leader fractal development model to obtain the mesoscopic topographic ground lightning distribution is as follows: The development of the lightning downlink leader fractal is simulated using COMSθL simulation software, such as... Figure 4As shown, first, the cloud potential, leader initiation position, and development step size are input. Then, the mountain height, mountain width, and other mountain modeling parameters are input. The potential and electric field intensity of each grid point in the mesoscale terrain are calculated. The position and potential of the potential development point of the lightning downlink leader are continuously calculated through the mesoscale terrain lightning downlink leader fractal development model. When the potential development point of the lightning downlink leader undergoes a jump, the simulation of one lightning strike process is completed. The above process is repeated until the simulation of t lightning strike processes is completed, and the coordinates of all lightning strike points are recorded to obtain the ground lightning distribution of the mesoscale terrain. In this paper, the judgment of the potential development point jump of the lightning downlink leader is as follows: when the average field strength between the uplink and downlink leaders or between the downlink leader and a target object that has not generated an uplink leader (an uplink leader refers to a phenomenon caused by a strong electric field on a target object, and the criterion is used to determine whether the target object generates an uplink leader) exceeds the average critical field strength of 500 kV / m, or when the uplink and downlink leaders meet, the final jump of the lightning strike occurs; the thundercloud potential is set to -200 MV; and the development step size is set to 20 m.

[0208] In the above technical solution, the specific method for calculating the lightning trip rate of transmission lines in complex terrain areas based on the ground flash density and lightning observation data of each area to be evaluated is as follows: The calculation formula for the backflashover trip rate based on the ground flash density and lightning observation data of each area to be evaluated is as follows:

[0209] P f =N×g×P I ×η

[0210]

[0211] In the formula, P f To represent the tripping rate, N is the total number of lightning strikes per year in the mesoscale terrain, g is the strike rate (1 / 6 for plains, 1 / 4 for mountains), and P... I Let I be the probability of a lightning current greater than I, and η be the arc-building rate, η = 0.4, N g The lightning density in each area of ​​the terrain to be evaluated is given by b, the distance between the two lightning rods is given by h, and the height of the lightning rod above the ground is given by h.

[0212] In the above technical solution, the calculation formula for the bypass tripping rate, obtained based on the ground flash density and lightning observation data of each area of ​​the terrain to be evaluated, is as follows:

[0213]

[0214] f(I)=I max (0.1r max ) 1.54

[0215] In the formula, P rLet N be the tripping rate due to the circuit breaker, η be the arc-building rate (η = 0.4), ΔL be the collector line segment of length ΔL, and N be the tripping rate due to the circuit breaker. g To assess the ground flash density in different terrain regions, I max I is the maximum current amplitude at which a flashover occurs. C For the amplitude of the lightning current, l BD Let f(I) be the lightning exposure width, f(I) be the lightning current probability density function, and r be the lightning current probability density function. max This represents the maximum distance for a circumferential strike.

[0216] In the above technical solution, the calculation formula for the induced lightning tripping rate, based on the ground flash density and lightning observation data of each area of ​​the terrain to be evaluated, is as follows:

[0217]

[0218] y max =25H C I / U 50％

[0219]

[0220]

[0221] In the formula, P g D is the tripping rate due to induced lightning. k r is the distance from the point of impact to the line. c For conductor striking distance, r g H is the ground impact distance. C y is the distance from the suspension point of the conductor on the tower to the ground. max U represents the flashover range of induced lightning, I represents the induced lightning current, and U represents the flashover range of induced lightning. 50％ 50% impulse flashover voltage of insulator string, N g Let I be the ground flash density in each area of ​​the terrain to be evaluated, and η be the arc-building rate, η = 0.4. C Let I be the amplitude of the lightning current, and P(I) be the probability function of the lightning current amplitude distribution.

[0222] In the above technical solution, the calculation formula for the lightning trip rate of transmission lines in each area of ​​the terrain to be evaluated, based on the backflashover trip rate, the bypass trip rate, and the induced lightning trip rate, is as follows:

[0223]

[0224] In the formula, S is the average lightning trip rate of each tower of the transmission line in each area of ​​the terrain to be evaluated, T is the total number of towers of the entire transmission line, m is the theoretical calculated lightning trip rate of the tower, m is the sum of backflash trip rate, backflash trip rate and induced lightning trip rate, and n is the number of towers.

[0225] In the above technical solution, the specific method for evaluating the lightning strike risk of each area in complex terrain through the lightning trip rate of the transmission line is as follows: when m < 0.5S, it is considered that the lightning strike risk level of the towers in each area of the complex terrain is Class I, and Class I is a low risk; when 0.5S < m < S, it is considered that the lightning strike risk level of the towers in each area of the complex terrain is Class II, and Class II is a medium risk; when S < m < 1.5S, it is considered that the lightning strike risk level of the towers in each area of the complex terrain is Class III, and Class III is a high risk; when m > 1.5S, it is considered that the lightning strike risk level of the towers in each area of the complex terrain is Class IV, and Class IV is an extremely high risk.

[0226] Embodiment 3

[0227] The third aspect of the present invention proposes a computer-readable storage medium, which stores a computer program, and when the computer program is executed by a processor, it implements the steps of the above method.

[0228] The present invention first selects a transmission line in a high-altitude mountainous area as the research object, uses a geographic information system to collect data on mesoscopic terrain within the transmission line corridor, calculates the change in cloud-to-ground flash density around the mountain body, establishes a mesoscopic terrain area, calculates the cloud-to-ground flash density within the mesoscopic area, and then based on the lightning-related data within the area, establishes a lightning fractal calculation model. At the same time, for the transmission line, considering the line position, ground inclination, and tower parameters, etc., a line model is established, and finally, the shielding failure, back flashover, and induced lightning trip rates of the transmission line are calculated. The lightning trip rate of each tower is calculated, and finally, the lightning strike risk assessment of the entire transmission line is completed.

[0229] Those skilled in the art should understand that the embodiments of the present invention can be provided as methods, systems, or computer-readable storage media. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer-readable storage medium implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0230] The present invention is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer-readable storage media according to the embodiments of the present invention. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, as well as the combination of flows and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate for implementation in the process Figure 1 One or more processes and / or boxes Figure 1 A system that specifies functions in one or more boxes.

[0231] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including an instruction set implemented in a process. Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0232] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0233] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit its scope of protection. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading the present invention, they can still make various changes, modifications or equivalent substitutions to the specific implementation of the invention, but these changes, modifications or equivalent substitutions are all within the scope of protection of the pending claims of the invention.

[0234] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

Claims

1. A lightning strike risk assessment system for power transmission lines, characterized in that, include: The topographic scale division module is used to divide the mountain and the flat area outside the mountain's critical area into several extraction segments. Based on the coefficient of variation of the ground flash density of the extraction segments and the average coefficient of variation of the ground flash density of the flat area, the boundary of the mesoscopic topography is divided, and the range from the boundary of the mesoscopic topography to the top of the mountain is divided into mesoscopic scale topography. The ground lightning distribution module is used to establish a mesoscopic terrain lightning downlink leader fractal development model based on the spatial electric field of the mesoscopic terrain. By simulating the mesoscopic terrain lightning downlink leader fractal development model, the ground lightning distribution of the mesoscopic terrain is obtained. The lightning risk assessment module is used to take the ground lightning distribution of the mesoscopic terrain as the ground flash density of each area of ​​the terrain to be assessed, calculate the lightning trip rate of the transmission lines in each area of ​​the terrain to be assessed based on the ground flash density and lightning observation data, and assess the lightning risk of each area of ​​the terrain to be assessed through the lightning trip rate of the transmission lines. The specific method for calculating the lightning trip rate of transmission lines in each area of ​​the terrain to be assessed based on the lightning density and lightning observation data is as follows: The calculation formula for the backflashover trip rate, obtained from the lightning density and lightning observation data of each area of ​​the terrain to be assessed, is as follows: P f =N×g×P I ×η (7) In the formula, P f To represent the tripping rate, N is the total number of lightning strikes per year in the mesoscale terrain, g is the strike rate (1 / 6 for plains, 1 / 4 for mountains), and P... I Let I be the probability of a lightning current greater than I, and η be the arc-building rate, η = 0.4, N g The lightning density in each area of ​​the terrain to be evaluated is given by b, the distance between the two lightning rods is given by h, and the height of the lightning rod above the ground is given by h. The calculation formula for the bypass tripping rate, based on the ground flash density and lightning observation data of each terrain region to be evaluated, is as follows: f(I)=I max (0.1r max ) 1.54 (10) In the formula, P r Let N be the tripping rate due to the circuit breaker, η be the arc-building rate (η = 0.4), ΔL be the collector line segment of length ΔL, and N be the tripping rate due to the circuit breaker. g To assess the ground flash density in different terrain regions, I max The maximum current amplitude at which a flashover occurs, l BD Let f(I) be the lightning exposure width, f(I) be the lightning current probability density function, and r be the lightning current probability density function. max This is the maximum circumduction distance; The formula for calculating the induced lightning tripping rate, based on the ground flash density and lightning observation data of each area of ​​the terrain to be evaluated, is as follows: y max =25H C I / U 50％ (12) In the formula, P g D is the tripping rate due to induced lightning. k r is the distance from the point of impact to the line. c For conductor striking distance, r g H is the ground impact distance. C y is the distance from the suspension point of the conductor on the tower to the ground. max U represents the flashover range of induced lightning, I represents the induced lightning current, and U represents the flashover range of induced lightning. 50％ 50% impulse flashover voltage of insulator string, N g Let I be the ground flash density in each area of ​​the terrain to be evaluated, and η be the arc-building rate, η = 0.

4. C Let I be the amplitude of the lightning current, and P(I) be the probability function of the lightning current amplitude distribution. Based on the backflashover tripping rate, the bypass tripping rate, and the induced lightning tripping rate, the calculation formulas for the lightning tripping rate of transmission lines in each area of ​​the terrain to be evaluated are as follows: In the formula, S is the average lightning trip rate of each tower of the transmission line in each area of ​​the terrain to be evaluated, T is the total number of towers of the entire transmission line, m is the theoretical calculated lightning trip rate of the tower, m is the sum of backflash trip rate, backflash trip rate and induced lightning trip rate, and n is the number of towers.

2. The transmission line lightning strike risk assessment system according to claim 1, characterized in that, The specific method for dividing the mountain and the flat area outside the mountain's critical zone into several extraction segments is as follows: the three-dimensional space formed by the width of the mountain, the height of the mountain, and the flat area outside the mountain's critical zone is used as the research space for mesoscopic topographic scale division, and the research space is divided into several extraction segments with the same distance along the extraction direction from the flat area to the mountain area.

3. The transmission line lightning strike risk assessment system according to claim 2, characterized in that, The specific method for delineating the boundary of mesoscopic topography based on the coefficient of variation of lightning density in the extracted sections and the average coefficient of variation of lightning density in the flat areas is as follows: calculate the coefficient of variation of lightning density in several extracted sections respectively, and compare the obtained coefficients of variation of lightning density in several extracted sections with the average coefficient of variation of lightning density in the flat areas within the study space. If the coefficient of variation of lightning density in the extracted section is greater than the coefficient of variation of lightning density in the flat areas, then the extracted section is the critical section of the mesoscopic topography scale within the study space, and the midpoint of the critical section is taken as the boundary of the mesoscopic topography.

4. The transmission line lightning strike risk assessment system according to claim 3, characterized in that, The specific method for establishing a mesoscale terrain lightning downward leader fractal development model based on the spatial electric field of the mesoscale terrain is as follows: Divide the mesoscale terrain into a grid with discrete grid points at equal intervals. The potential relationship of the spatial electric field formed by each discrete grid point in the grid is shown in the following formula: In the formula, Let $\frac{i}{j}$ be the potential of the grid point in the $i$-th row and $j$-th column. Let $\frac{i+1}{j}$ be the potential of the grid point in the (i+1)th row and the (j)th column. Let $\frac{i}{j+1}$ be the potential of the grid point in the $i$-th row and $j+1$-th column. Let $\frac{i}{j-1}$ be the potential of the grid point in the $i$-th row and $j-1$-th column. Let be the potential of the grid point in the (i-1)th row and jth column of the grid; Perform calculations on Equation (1) using the successive over-relaxation iteration method, and the potential relationship of the spatial electric field of the grid after iteration is shown in the following formula: In the formula, After the nth iteration The value of ω, where ω is the relaxation factor. After the (n+1)th iteration The value, After the (n+1)th iteration The value, After the (n+1)th iteration The value, After the (n+1)th iteration The value, After the (n+1)th iteration The value; The calculation formula for the optimal relaxation factor that makes the iteration process converge fastest in Equation (2) is shown in the following formula: In the formula, ω0 is the optimal relaxation factor, and n and m are the number of grids divided on the long and wide sides of the mesoscale terrain in the rectangular area, respectively; Judge the potential development points of the lightning downward leader according to the grid points of the lightning discharge channel inside the mesoscale terrain. The judgment formula is shown as follows: In the formula, E is the average field strength between the discharge grid points inside the lightning discharge channel and the potential development point of the lightning downward leader. Let E be the potential difference between the discharge grid points inside the lightning discharge channel and the potential development point of the downward lightning leader, and let L be the actual distance between the discharge grid points inside the lightning discharge channel and the potential development point of the downward lightning leader. c E is the critical discharge field strength. c =216kV / m; The probability of the potential development point of the lightning downward leader developing is shown in the following formula: In the formula, The development of discharge grid point N within the lightning discharge channel into potential development point N of the downlink lightning leader. * The probability, From the discharge grid point N inside the lightning discharge channel to the potential development point N of the downlink lightning leader. * The electric field strength between them, where η is the development probability exponent, E c E is the critical discharge field strength. c =216kV / m; If the potential development point of the lightning downward leader develops into a grid point inside a new lightning discharge channel, the potential calculation formula for the potential development point of the lightning downward leader is as follows: In the formula, To develop into a potential development point N for a new lightning downlink leader within a lightning discharge channel. * The potential, E represents the potential of discharge grid point N within the lightning discharge channel. ch The electric field strength inside the new lightning discharge channel. From discharge grid point N to potential development point N * The distance between them.

5. The transmission line lightning strike risk assessment system according to claim 4, characterized in that, The specific method for obtaining the ground lightning strike distribution of the mesoscale terrain through simulation calculation of the mesoscale terrain lightning downward leader fractal development model is as follows: Calculate the potential and electric field intensity of each grid point in the mesoscale terrain, and continuously calculate the position and potential of the potential development points of the lightning downward leader through the mesoscale terrain lightning downward leader fractal development model. When a jump occurs at the potential development point of the lightning downward leader, the simulation of one lightning strike process is completed. Repeat the above process until the simulation of t lightning strike processes is completed, and record the coordinates of all lightning strike points to obtain the ground lightning strike distribution of the mesoscale terrain.

6. The transmission line lightning strike risk assessment system according to claim 1, characterized in that, The specific method for evaluating the lightning strike risk of each region of the terrain to be evaluated through the lightning strike tripping rate of the transmission line is as follows: When m < 0.5S, it is considered that the lightning strike risk level of the transmission towers in each region of the terrain to be evaluated is Class I; When 0.5S < m < S, it is considered that the lightning strike risk level of the transmission towers in each region of the terrain to be evaluated is Class II; When S < m < 1.5S, it is considered that the lightning strike risk level of the transmission towers in each region of the terrain to be evaluated is Class III; When m > 1.5S, it is considered that the lightning strike risk level of the transmission towers in each region of the terrain to be evaluated is Class IV.

7. A method for assessing the lightning strike risk of transmission lines, characterized in that, It includes: Divide the mountain body and the flat area outside the critical area of the mountain body into several extraction sections, divide the boundary of the mesoscale terrain according to the coefficient of variation of the cloud-to-ground flash density of the extraction section, and divide the range from the boundary of the mesoscale terrain to the vertex of the mountain body into the mesoscale terrain; Establish a mesoscale terrain lightning downward leader fractal development model based on the spatial electric field of the mesoscale terrain, and obtain the ground lightning strike distribution of the mesoscale terrain through simulation calculation of the mesoscale terrain lightning downward leader fractal development model; Use the ground lightning strike distribution of the mesoscale terrain as the cloud-to-ground flash density of each region of the terrain to be evaluated, calculate the lightning strike tripping rate of the transmission line in each region of the terrain to be evaluated according to the cloud-to-ground flash density and lightning observation data of each region of the terrain to be evaluated, and evaluate the lightning strike risk of each region of the terrain to be evaluated through the lightning strike tripping rate of the transmission line; The specific method for calculating the lightning trip rate of transmission lines in each area of ​​the terrain to be assessed based on the lightning density and lightning observation data is as follows: The calculation formula for the backflashover trip rate, obtained from the lightning density and lightning observation data of each area of ​​the terrain to be assessed, is as follows: P f =N×g×P I ×η (7) In the formula, P f To represent the tripping rate, N is the total number of lightning strikes per year in the mesoscale terrain, g is the strike rate (1 / 6 for plains, 1 / 4 for mountains), and P... I Let I be the probability of a lightning current greater than I, and η be the arc-building rate, η = 0.4, N g The lightning density in each area of ​​the terrain to be evaluated is given by b, the distance between the two lightning rods is given by h, and the height of the lightning rod above the ground is given by h. The calculation formula for the bypass tripping rate, based on the ground flash density and lightning observation data of each terrain region to be evaluated, is as follows: f(I)=I max (0.1r max ) 1.54 (10) In the formula, P r Let N be the tripping rate due to the circuit breaker, η be the arc-building rate (η = 0.4), ΔL be the collector line segment of length ΔL, and N be the tripping rate due to the circuit breaker. g To assess the ground flash density in different terrain regions, I max I is the maximum current amplitude at which a flashover occurs. C For the amplitude of the lightning current, l BD Let f(I) be the lightning exposure width, f(I) be the lightning current probability density function, and r be the lightning current probability density function. max This is the maximum circumduction distance; The formula for calculating the induced lightning tripping rate, based on the ground flash density and lightning observation data of each area of ​​the terrain to be evaluated, is as follows: y max =25H C I / U 50％ (12) In the formula, P g D is the tripping rate due to induced lightning. k r is the distance from the point of impact to the line. c For conductor striking distance, r g H is the ground impact distance. C y is the distance from the suspension point of the conductor on the tower to the ground. max U represents the flashover range of induced lightning, I represents the induced lightning current, and U represents the flashover range of induced lightning. 50％ 50% impulse flashover voltage of insulator string, N g Let I be the ground flash density in each area of ​​the terrain to be evaluated, and η be the arc-building rate, η = 0.

4. C Let I be the amplitude of the lightning current, and P(I) be the probability function of the lightning current amplitude distribution. Based on the backflashover tripping rate, the bypass tripping rate, and the induced lightning tripping rate, the calculation formulas for the lightning tripping rate of transmission lines in each area of ​​the terrain to be evaluated are as follows: In the formula, S is the average lightning trip rate of each tower of the transmission line in each area of ​​the terrain to be evaluated, T is the total number of towers of the entire transmission line, m is the theoretical calculated lightning trip rate of the tower, m is the sum of backflash trip rate, backflash trip rate and induced lightning trip rate, and n is the number of towers.

8. The method for assessing the lightning strike risk of transmission lines according to claim 7, characterized in that, The specific method for dividing the mountain and the flat area outside the mountain's critical zone into several extraction segments is as follows: the three-dimensional space formed by the width of the mountain, the height of the mountain, and the flat area outside the mountain's critical zone is used as the research space for mesoscopic topographic scale division, and the research space is divided into several extraction segments with the same distance along the extraction direction from the flat area to the mountain area.

9. The method for assessing the lightning strike risk of transmission lines according to claim 8, characterized in that, The specific method for delineating the boundary of mesoscopic topography based on the coefficient of variation of lightning density in the extracted sections and the average coefficient of variation of lightning density in the flat areas is as follows: calculate the coefficient of variation of lightning density in several extracted sections respectively, and compare the obtained coefficients of variation of lightning density in several extracted sections with the average coefficient of variation of lightning density in the flat areas within the study space. If the coefficient of variation of lightning density in the extracted section is greater than the coefficient of variation of lightning density in the flat areas, then the extracted section is the critical section of the mesoscopic topography scale within the study space, and the midpoint of the critical section is taken as the boundary of the mesoscopic topography.

10. The method for assessing the lightning strike risk of transmission lines according to claim 9, characterized in that, The specific method for establishing a mesoscale terrain lightning downlink leader fractal development model based on the spatial electric field of the mesoscale terrain is as follows: the mesoscale terrain is divided into a grid of discrete grid points with equal spacing, and the potential relationship of the spatial electric field formed by each discrete grid point within the grid is shown in the following formula: In the formula, Let $\frac{i}{j}$ be the potential of the grid point in the $i$-th row and $j$-th column. Let $\frac{i+1}{j}$ be the potential of the grid point in the (i+1)th row and the (j)th column. Let $\frac{i}{j+1}$ be the potential of the grid point in the $i$-th row and $j+1$-th column. Let $\frac{i}{j-1}$ be the potential of the grid point in the $i$-th row and $j-1$-th column. Let be the potential of the grid point in the (i-1)th row and jth column of the grid; Equation (1) is calculated using the over-relaxation iteration method, and the potential relationship of the spatial electric field of the mesh after iteration is shown in the following equation: In the formula, After the nth iteration The value of ω, where ω is the relaxation factor. After the (n+1)th iteration The value, After the (n+1)th iteration The value, After the (n+1)th iteration The value, After the (n+1)th iteration The value, After the (n+1)th iteration The value; The formula for calculating the optimal relaxation factor that makes the iterative process converge fastest in equation (2) is as follows: In the formula, ω0 is the optimal relaxation factor, and n and m are the number of grids divided on both the length and width sides of the mesoscopic-scale terrain within the rectangular region, respectively. The potential development point of the downlink lightning leader is determined based on the discharge grid points inside the lightning discharge channel in the mesoscale topography, and the determination formula is as follows: In the formula, E is the average field strength between the discharge grid points inside the lightning discharge channel and the potential development point of the lightning downward leader. Let E be the potential difference between the discharge grid points inside the lightning discharge channel and the potential development point of the downward lightning leader, and let L be the actual distance between the discharge grid points inside the lightning discharge channel and the potential development point of the downward lightning leader. c E is the critical discharge field strength. c =216kV / m; The probability of a potential development point for a downlink lightning leader is shown in the following formula: In the formula, The development of discharge grid point N within the lightning discharge channel into potential development point N of the downlink lightning leader. * The probability, From the discharge grid point N inside the lightning discharge channel to the potential development point N of the downlink lightning leader. * The electric field strength between them, where η is the development probability exponent, E c E is the critical discharge field strength. c =216kV / m; If a potential development point of a downlink lightning leader develops into a discharge grid point within a new lightning discharge channel, the potential calculation formula for the potential development point of the downlink lightning leader is as follows: In the formula, To develop into a potential development point N for a new lightning downlink leader within a lightning discharge channel. * The potential, E represents the potential of discharge grid point N within the lightning discharge channel. ch The electric field strength inside the new lightning discharge channel. From discharge grid point N to potential development point N * The distance between them.

11. The method for assessing the lightning strike risk of transmission lines according to claim 10, characterized in that, The specific method for obtaining the mesoscale terrain ground lightning strike distribution by performing simulation calculations on the mesoscale terrain lightning downward leader fractal development model is as follows: Calculate the potential and electric field intensity of each grid point in the mesoscale terrain, and continuously calculate the position and potential of the potential development points of the lightning downward leader through the mesoscale terrain lightning downward leader fractal development model. When a jump occurs at the potential development point of the lightning downward leader, the simulation of one lightning strike process is completed. Repeat the above process until the simulation of t lightning strike processes is completed, and record the coordinates of all lightning strike points to obtain the mesoscale terrain ground lightning strike distribution.

12. The method for assessing the lightning strike risk of transmission lines according to claim 7, characterized in that, The specific method for evaluating the lightning strike risk of each region of the terrain to be evaluated through the lightning strike tripping rate of the transmission line is as follows: When m < 0.5S, it is considered that the lightning strike risk level of the poles and towers in each region of the terrain to be evaluated is Class I; When 0.5S < m < S, it is considered that the lightning strike risk level of the poles and towers in each region of the terrain to be evaluated is Class II; When S < m < 1.5S, it is considered that the lightning strike risk level of the poles and towers in each region of the terrain to be evaluated is Class III; When m > 1.5S, it is considered that the lightning strike risk level of the poles and towers in each region of the terrain to be evaluated is Class IV.

13. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, it implements the steps of the method described in any one of claims 7-12.

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