A method for intelligently extracting geometric parameters of an electric transmission channel EGM model

Abstract

This invention discloses an intelligent method for extracting geometric parameters of an EGM model for a power transmission channel, including the extraction of line structure parameters, comprising: automatically extracting the point sets of the side-phase conductors on both sides; automatically extracting the outer upper side of the side-phase conductors to be evaluated as a split line; and extracting the point sets S of the left and right lightning protection wires. L S R Perform linear fitting on the XOY surface and parabolic fitting on the XOZ surface; automatically pair the fitted conductor and lightning protection wire equations according to the marked positional relationships; substitute the x-coordinates of the calculated points into the spatial curve equations of the paired conductors and ground wires to obtain the coordinates (y-coordinates) of the conductor and lightning protection wire points within the cross-section. c ,z c ), (y s ,z s ), calculate the height difference h between the conductor and the ground wire. sc and horizontal spacing d sc The invention can autonomously identify the conductor to be evaluated and filter the required sample point cloud for parameter extraction. It can automatically extract and pair the conductor and lightning protection wire according to their spatial location, thereby improving the accuracy and efficiency of line structure parameter measurement.

Description

Technical Field

[0001] This invention belongs to the field of power transmission technology, specifically relating to an intelligent method for extracting geometric parameters of the EGM model of a power transmission channel. Background Technology

[0002] Lightning strikes are one of the main threats to the safe operation of ultra-high voltage (UHV) and extra-high voltage (EHV) overhead lines. With the continuous construction and commissioning of UHV lines, strike prevention has attracted great attention from power grid companies. The concept of "differentiated lightning protection" suggests that conducting strike risk assessments based on differentiated factors such as topography, line structure, and lightning activity helps identify weaknesses in line lightning protection and improves the technical and economic efficiency of strike prevention. Phase-specific and comprehensive strike risk assessments are of great significance for UHV and EHV line lightning protection.

[0003] Currently, the widely used quantitative calculation model for backflashover risk is the electro-geometric model (EGM), which comprehensively considers the influence of line structure and topography through geometric parameters. In the past, ground elevation databases and tower drawings were used as data sources for parameter extraction, but the accuracy and precision of the geometric parameters were limited, and they are no longer suitable for the needs of differentiated and refined assessment of backflashover risk. Researching advanced parameter extraction algorithms is a necessary condition for achieving differentiated and refined assessment of backflashover risk.

[0004] With the continuous development of 3D real-scene reconstruction technology, the point cloud data collected by airborne LiDAR can achieve centimeter-level accuracy, providing technical support for the precise digital description of power transmission channels. However, in practical engineering, the difficulty of parameter extraction based on LiDAR lies in the following: LiDAR generates massive amounts of discrete and irregular point cloud data, making it difficult to ensure the accuracy of parameter extraction; refined evaluation of the entire channel requires parameter extraction at a large number of locations, and manual operation greatly limits the evaluation precision. In the past, the identification of a single power line relied on manual operation, resulting in low efficiency in extracting line structure parameters. Summary of the Invention

[0005] The purpose of this invention is to provide an intelligent method for extracting geometric parameters of the EGM model of a power transmission channel, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for intelligent extraction of geometric parameters of an EGM model for power transmission channels, comprising the extraction of line structure parameters, wherein the extraction of line structure parameters includes the following steps:

[0007] S1: First, segment the three-phase conductor point cloud to obtain three-phase conductor point sets C1, C2, and C3, and use (x) uniformly. C y C , z C() represents the average coordinates of point set C, which is automatically extracted from the point sets of the two side phase conductors by the formula;

[0008] S2: Divide the split line of a single-phase conductor. Taking a 4-split conductor as an example, obtain the set of points C of the split line of the left phase. L1 C L2 C L3 C L4 ∈C L ; Right-side splitting line point set C R1 C R2 C R3 C R4 ∈C R The formula automatically extracts the outer upper side split line to be evaluated from the phase conductor;

[0009] S3: Using the above method, the lightning protection wire point cloud is automatically segmented and extracted to obtain the left and right lightning protection wire point sets S. L S R ;

[0010] S4: Finally, pair the set of guide points C LP C RP And lightning protection line point set S L S R Perform linear fitting on the XOY surface and parabolic fitting on the XOZ surface;

[0011] S5: The fitted conductor and lightning protection wire equations are automatically matched according to the positional relationships marked above;

[0012] S6: Then substitute the x-coordinate of the calculated point into the spatial curve equation of the paired conductor and ground wire to obtain the coordinates (y-coordinates) of the conductor and lightning protection wire points within the cross section. c ,z c ), (y s ,z s ), calculate the height difference h between the conductor and the ground wire. sc and horizontal spacing d sc The measured value.

[0013] Preferably, in step S1, the point cloud data of the power transmission channel is defined with the X-axis as the direction along the line, the Y-axis as the direction across the line, and the Z-axis as the vertical direction, with the negative Y-axis as the left side of the line and the positive Y-axis as the right side of the line.

[0014] Preferably, in any of the above solutions, in step S1, the formula is:

[0015] In the formula: C L C R These are the sets of points for the left and right phase conductors, respectively.

[0016] Preferably, in step S2, the formula is:

[0017] In the formula: C LP C RP These are the sets of split line points to be evaluated on the outer upper side of the left and right phase conductors, respectively.

[0018] In any of the above schemes, it is preferred that, in step S4, the parameters are determined using the least squares method, and the space curve equation is in the form of:

[0019] In any of the above schemes, it is preferred that, in step S5, the calculation of the conductor-to-ground wire height difference h... sc and horizontal spacing d sc The measured value is obtained using the formula

[0020] The technical effects and advantages of this invention are as follows: The intelligent extraction method for geometric parameters of the EGM model of the power transmission channel can realize the automatic extraction of the point cloud of the target line. The proposed method can accurately identify split conductors, improve the extraction efficiency of line structure parameters, autonomously identify the conductors to be evaluated and screen the sample point clouds required for parameter extraction, and automatically extract and match the conductors to be evaluated and lightning protection wires according to their spatial positions, thereby improving the measurement accuracy and efficiency of line structure parameters. Attached Figure Description

[0021] Figure 1 This is a diagram showing the spatial relationship of the circuit in this invention;

[0022] Figure 2 This is a flowchart illustrating the automated parameter extraction process of this invention. Detailed Implementation

[0023] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0024] Geometric parameters of EGM model

[0025] According to IEEE Working Group 1243-1997 standard

[18] The EGM model calculates the flashover rate using the following formula:

[0026]

[0027] In the formula: S F The flashover rate is expressed as times per (100 km·a); N g Ground flashover density, times / (km)2 ·a); I c Minimum flashover current, kA; I max Maximum winding current, kA; D c (I) represents the exposure distance in meters; f(I) represents the probability density function of the lightning current amplitude.

[0028] The EGM model uses strike distance to characterize an object's ability to attract lightning; the strike distance formula is:

[0029]

[0030] In the formula: r s r c r g These represent the strike distances of the lightning conductor, ground conductor, and ground, respectively, in meters (m); I is the lightning current amplitude, in kA; h c The height of the conductor above the ground is in meters (m).

[0031] Exposure distance Dc is an important intermediate variable in calculating the flashover rate, determined by the spatial location and strike distance range of the lightning conductor, the ground conductor, and the ground wire. Line structural parameters describe the spatial relationship between the ground wire and the conductor, including the conductor-to-ground wire height difference h. sc Horizontal spacing d of conductors sc Topographic parameters are used to describe the spatial relationship between the conductor and the ground, including the conductor's height h above the ground. c The ground inclination angle is θ. Based on the shielding relationship, it can be seen that the edge phase conductors require one set each of line structure parameters and terrain parameters; the middle phase conductors require two sets of line structure parameters.

[0032] Based on the above theoretical analysis, the intelligent extraction algorithm for geometric parameters of the EGM model of the transmission channel proposed in this paper is as follows: After the point cloud of the transmission channel of a single span is classified, the line and the ground are selected; the conductor and ground wire point set required for evaluation is extracted by autonomous segmentation using spatial location features, curve fitting is performed using the least squares method, and the line structure parameters are extracted based on the curve equation; the ground is automatically sampled using a specific three-dimensional sliding window according to the conductor position, and the protrusion discrimination condition is constructed to classify flat terrain and protruding terrain, and the terrain and landform parameters are extracted.

[0033] This algorithm can intelligently extract parameters from phase conductors by recognizing target point clouds. The following section primarily focuses on the edge phase conductors, illustrating the intelligent extraction algorithm for line structure parameters and topographic parameters, including the line structure parameter extraction algorithm required for evaluating intermediate phase conductors. For ease of description, the transmission channel point cloud data is defined with the X-axis representing the direction along the line (tower connection), the Y-axis representing the direction across the line, and the Z-axis representing the vertical direction; the negative Y-axis represents the left side of the line, and the positive Y-axis represents the right side of the line.

[0034] Line structure parameter extraction

[0035] Research on power line point cloud reconstruction is relatively mature. To extract the line structure at any location within the channel, the mainstream approach is to segment, identify, and fit the conductor and ground wire point clouds. Fitting models include parabolic and catenary models. Literature experimental results show that using the parabolic equation for power line point cloud fitting has higher efficiency and accuracy. However, previous identification of single power lines relied on manual operation. To improve the efficiency of line structure parameter extraction, the focus of this paper is on achieving automatic extraction of target line point clouds. The proposed method can accurately identify split conductors.

[0036] To reduce corona loss, ultra-high voltage (UHV) and extra-high voltage (EHV) transmission lines typically use split conductors. In the EGM model, the bundle of split conductors furthest from the lightning protection wire and ground shield poses the greatest risk of snagging, making it a reasonable choice for evaluation. Figure 1 As can be seen, conductors / ground wires at different locations exhibit significant differences in spatial coordinates. The automatic extraction process of lines and extraction of line structure parameters based on spatial location relationships is as follows:

[0037] First, the point cloud of the three-phase conductors is segmented to obtain the three-phase conductor point sets C1, C2, and C3. (x...) C y C , z C ) represents the average coordinates of point set C, and the point sets of the two side phase conductors are automatically extracted by the following formula.

[0038]

[0039] In the formula: C L C R These are the sets of points for the left and right phase conductors, respectively.

[0040] Then, the split line of the single-phase conductor is divided. Taking a 4-split conductor as an example, the set of points C of the left-side phase split line is obtained. L1 C L2 C L3 C L4 ∈C L ; Right-side splitting line point set C R1 C R2 C R3 C R4 ∈C R The outer upper side split line to be evaluated of the edge phase conductor is automatically extracted by the following formula.

[0041]

[0042] In the formula: C LP C RP These are the sets of split line points to be evaluated on the outer upper side of the left and right phase conductors, respectively.

[0043] Similarly, the point cloud of the lightning protection wires is automatically segmented and extracted to obtain the left and right lightning protection wire point sets S. L S R .

[0044] Finally, the set of guide points C is... LP C RP And lightning protection line point set S L S R Linear fitting to the XOY surface and parabolic fitting to the XOZ surface are performed, and the parameters are determined using the least squares method. The space curve equation is in the form of:

[0045]

[0046] For a given conductor calculation point, the shielding effect of the lightning rod mainly comes from the horizontal direction of the conductor. Therefore, a cross-section is set based on the x-coordinate of the conductor calculation point, and the intersection of the lightning rods is taken as the position representing the strongest shielding effect. To determine the intersection point of the spatial parabola at the cross-section, the fitted conductor and lightning rod equations are first automatically paired according to the positional relationship marked above. Then, the x-coordinate of the calculation point is substituted into the spatial curve equation of the paired conductor and ground wire to obtain the coordinates (y, y) of the conductor and lightning rod points within the cross-section. c ,z c ), (y s ,z s The elevation difference h between the conductor and the ground wire is calculated using the following formula. sc and horizontal spacing d sc The measured value.

[0047]

[0048] Building upon existing research on power line segmentation, the aforementioned method enables the automatic extraction and pairing of conductors and lightning protection wires to be evaluated based on their spatial location, thereby improving the accuracy and efficiency of line structure parameter measurement. If tension towers exist in the span to be evaluated, the jumpers at the tension towers are individually segmented and fitted. Since the jumpers are also in a suspended state, the same automatic algorithm as for the conductors is used for extraction, fitting, and parameter measurement.

[0049] For continuous conductor-ground line spatial curves, cross-sectional sampling is used, while for discrete ground point cloud data, three-dimensional sampling spatial sampling is used. This makes parameter extraction feasible at any position in the entire channel, and the direct measurement method can effectively improve the accuracy of parameter extraction, thus possessing the basic conditions for full-channel small-granular traversal evaluation.

[0050] For the traverse to be evaluated, a series of calculation points are set along the positive X-axis with a small granularity Q (e.g., 1m) in the direction of the traverse, forming a parameter extraction calculation queue. The sampling width W is set to be greater than the granularity Q of the calculation points, so that the terrain sampling of adjacent calculation points overlaps, thereby achieving the extraction of terrain parameters without omissions across the entire channel.

[0051] Furthermore, lightning discharge is random, and actual lightning strikes do not strictly occur within a single cross-section. For a given conductor calculation point, the lightning leader development path causing the strike tends to pass over weakly shielded terrain. To more comprehensively consider the shielding effect of the surrounding terrain, a "one-to-many" rolling calculation method for strike risk is adopted. This involves sequentially combining the line structure at a given calculation point with the terrain parameters of P adjacent calculation points to perform multiple rolling EGM model calculations, and taking the maximum value of the evaluation result as the strike risk at that conductor calculation point.

[0052] The risk of entanglement at the i-th conductor point is calculated using the following formula.

[0053] S F =max{S F1 ,S F2 ,S F3} (16)

[0054] In the formula: S F1 S F2 ,S F3 These are the flashover rates calculated by combining the (i+1)th, ith, and (i-1)th topographic parameters with the ith line structure parameter, respectively.

[0055] A comprehensive and thorough evaluation covering all channels implies a large number of cross-sections, rendering current manual operations inapplicable. An automated operation process needs to be designed. (See [link to automated operation process]). Figure 2 As shown, by inputting the point cloud of the transmission channel, the automated parameter extraction operation can be completed to obtain the geometric parameters of the phase conductors throughout the channel. This automated process achieves precise phase-by-phase and refined full-channel parameter extraction by sequentially generating calculation queues for each conductor object and traversing all calculation queues.

[0056] The algorithm completes parameter extraction and circumvention risk assessment with small-granularity automatic traversal. The research results can serve as data support for circumvention risk classification analysis. Previous circumvention risk assessments were conducted on a per-span / tower basis. The algorithm proposed in this paper can achieve fine-grained classification of risk levels at different locations within each span.

[0057] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for intelligent extraction of geometric parameters of EGM model of power transmission channel, characterized in that: This includes the extraction of line structure parameters, which comprises the following steps: S1: First, segment the three-phase conductor point cloud to obtain three-phase conductor point sets C1, C2, and C3, and use (x) uniformly. C y C , z C () represents the average coordinates of point set C, which is automatically extracted from the point sets of the two side phase conductors by the formula; S2: Divide the split line of the single-phase conductor into four split lines, and obtain the set of split line points C on the left side. L1 C L2 C L3 C L4 ∈C L ; Right-side splitting line point set C R1 C R2 C R3 C R4 ∈C R The formula automatically extracts the outer upper side split line to be evaluated from the phase conductor; S3: Using the above method, the lightning protection wire point cloud is automatically segmented and extracted to obtain the left and right lightning protection wire point sets S. L S R ; S4: Finally, pair the set of guide points C LP C RP And lightning protection line point set S L S R Perform linear fitting on the XOY surface and parabolic fitting on the XOZ surface; In step S4, the parameters are determined using the least squares method, and the space curve equation is in the form of: S5: The fitted conductor and lightning protection wire equations are automatically matched according to the positional relationships marked above; S6: Then substitute the x-coordinate of the calculated point into the spatial curve equation of the paired conductor and ground wire to obtain the coordinates (y-coordinates) of the conductor and lightning protection wire points within the cross section. c ,z c ), (y s ,z s ), calculate the height difference h between the conductor and the ground wire. sc and horizontal spacing d sc The measured value.

2. The intelligent extraction method for geometric parameters of EGM model of power transmission channel according to claim 1, characterized in that: In step S1, it is specified that the point cloud data of the power transmission channel is oriented with the X-axis as the direction along the line, the Y-axis as the direction across the line, and the Z-axis as the vertical direction, with the negative Y-axis as the left side of the line and the positive Y-axis as the right side of the line.

3. The intelligent extraction method for geometric parameters of EGM model of power transmission channel according to claim 1, characterized in that: In step S1, the formula is: In the formula: C L C R These are the sets of points for the left and right phase conductors, respectively.

4. The intelligent extraction method for geometric parameters of EGM model of power transmission channel according to claim 1, characterized in that: In step S2, the formula is: In the formula: C LP C RP These are the sets of split line points to be evaluated on the outer upper side of the left and right phase conductors, respectively.

5. The intelligent extraction method for geometric parameters of EGM model of power transmission channel according to claim 1, characterized in that: In step S5, the calculation of the conductor-to-ground wire height difference h sc and horizontal spacing d sc The measured value is obtained using the formula .

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